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<div class="section" id="command-line-and-environment">
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<span id="using-on-general"></span><h1>1. Command line and environment<a class="headerlink" href="#command-line-and-environment" title="Permalink to this headline">¶</a></h1>
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<p>The CPython interpreter scans the command line and the environment for various
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<div class="section" id="command-line">
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<span id="using-on-cmdline"></span><h2>1.1. Command line<a class="headerlink" href="#command-line" title="Permalink to this headline">¶</a></h2>
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<p>When invoking Python, you may specify any of these options:</p>
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<div class="highlight-sh notranslate"><div class="highlight"><pre><span></span>python <span class="o">[</span>-bBdEhiIOqsSuvVWx?<span class="o">]</span> <span class="o">[</span>-c <span class="nb">command</span> <span class="p">|</span> -m module-name <span class="p">|</span> script <span class="p">|</span> - <span class="o">]</span> <span class="o">[</span>args<span class="o">]</span>
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</pre></div>
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</div>
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<p>The most common use case is, of course, a simple invocation of a script:</p>
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<div class="highlight-sh notranslate"><div class="highlight"><pre><span></span>python myscript.py
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||
</pre></div>
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</div>
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<div class="section" id="interface-options">
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<span id="using-on-interface-options"></span><h3>1.1.1. Interface options<a class="headerlink" href="#interface-options" title="Permalink to this headline">¶</a></h3>
|
||
<p>The interpreter interface resembles that of the UNIX shell, but provides some
|
||
additional methods of invocation:</p>
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||
<ul class="simple">
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<li><p>When called with standard input connected to a tty device, it prompts for
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||
commands and executes them until an EOF (an end-of-file character, you can
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produce that with <kbd class="kbd docutils literal notranslate">Ctrl-D</kbd> on UNIX or <kbd class="kbd docutils literal notranslate">Ctrl-Z, Enter</kbd> on Windows) is read.</p></li>
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<li><p>When called with a file name argument or with a file as standard input, it
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reads and executes a script from that file.</p></li>
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<li><p>When called with a directory name argument, it reads and executes an
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appropriately named script from that directory.</p></li>
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<li><p>When called with <code class="docutils literal notranslate"><span class="pre">-c</span> <span class="pre">command</span></code>, it executes the Python statement(s) given as
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||
<em>command</em>. Here <em>command</em> may contain multiple statements separated by
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||
newlines. Leading whitespace is significant in Python statements!</p></li>
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<li><p>When called with <code class="docutils literal notranslate"><span class="pre">-m</span> <span class="pre">module-name</span></code>, the given module is located on the
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||
Python module path and executed as a script.</p></li>
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||
</ul>
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||
<p>In non-interactive mode, the entire input is parsed before it is executed.</p>
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||
<p>An interface option terminates the list of options consumed by the interpreter,
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||
all consecutive arguments will end up in <a class="reference internal" href="../library/sys.html#sys.argv" title="sys.argv"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.argv</span></code></a> – note that the first
|
||
element, subscript zero (<code class="docutils literal notranslate"><span class="pre">sys.argv[0]</span></code>), is a string reflecting the program’s
|
||
source.</p>
|
||
<dl class="cmdoption">
|
||
<dt id="cmdoption-c">
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||
<code class="descname">-c</code><code class="descclassname"> <command></code><a class="headerlink" href="#cmdoption-c" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Execute the Python code in <em>command</em>. <em>command</em> can be one or more
|
||
statements separated by newlines, with significant leading whitespace as in
|
||
normal module code.</p>
|
||
<p>If this option is given, the first element of <a class="reference internal" href="../library/sys.html#sys.argv" title="sys.argv"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.argv</span></code></a> will be
|
||
<code class="docutils literal notranslate"><span class="pre">"-c"</span></code> and the current directory will be added to the start of
|
||
<a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a> (allowing modules in that directory to be imported as top
|
||
level modules).</p>
|
||
</dd></dl>
|
||
|
||
<dl class="cmdoption">
|
||
<dt id="cmdoption-m">
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||
<code class="descname">-m</code><code class="descclassname"> <module-name></code><a class="headerlink" href="#cmdoption-m" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Search <a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a> for the named module and execute its contents as
|
||
the <a class="reference internal" href="../library/__main__.html#module-__main__" title="__main__: The environment where the top-level script is run."><code class="xref py py-mod docutils literal notranslate"><span class="pre">__main__</span></code></a> module.</p>
|
||
<p>Since the argument is a <em>module</em> name, you must not give a file extension
|
||
(<code class="docutils literal notranslate"><span class="pre">.py</span></code>). The module name should be a valid absolute Python module name, but
|
||
the implementation may not always enforce this (e.g. it may allow you to
|
||
use a name that includes a hyphen).</p>
|
||
<p>Package names (including namespace packages) are also permitted. When a
|
||
package name is supplied instead
|
||
of a normal module, the interpreter will execute <code class="docutils literal notranslate"><span class="pre"><pkg>.__main__</span></code> as
|
||
the main module. This behaviour is deliberately similar to the handling
|
||
of directories and zipfiles that are passed to the interpreter as the
|
||
script argument.</p>
|
||
<div class="admonition note">
|
||
<p class="admonition-title">Note</p>
|
||
<p>This option cannot be used with built-in modules and extension modules
|
||
written in C, since they do not have Python module files. However, it
|
||
can still be used for precompiled modules, even if the original source
|
||
file is not available.</p>
|
||
</div>
|
||
<p>If this option is given, the first element of <a class="reference internal" href="../library/sys.html#sys.argv" title="sys.argv"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.argv</span></code></a> will be the
|
||
full path to the module file (while the module file is being located, the
|
||
first element will be set to <code class="docutils literal notranslate"><span class="pre">"-m"</span></code>). As with the <a class="reference internal" href="#cmdoption-c"><code class="xref std std-option docutils literal notranslate"><span class="pre">-c</span></code></a> option,
|
||
the current directory will be added to the start of <a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a>.</p>
|
||
<p>Many standard library modules contain code that is invoked on their execution
|
||
as a script. An example is the <a class="reference internal" href="../library/timeit.html#module-timeit" title="timeit: Measure the execution time of small code snippets."><code class="xref py py-mod docutils literal notranslate"><span class="pre">timeit</span></code></a> module:</p>
|
||
<div class="highlight-sh notranslate"><div class="highlight"><pre><span></span>python -mtimeit -s <span class="s1">'setup here'</span> <span class="s1">'benchmarked code here'</span>
|
||
python -mtimeit -h <span class="c1"># for details</span>
|
||
</pre></div>
|
||
</div>
|
||
<div class="admonition seealso">
|
||
<p class="admonition-title">See also</p>
|
||
<dl class="simple">
|
||
<dt><a class="reference internal" href="../library/runpy.html#runpy.run_module" title="runpy.run_module"><code class="xref py py-func docutils literal notranslate"><span class="pre">runpy.run_module()</span></code></a></dt><dd><p>Equivalent functionality directly available to Python code</p>
|
||
</dd>
|
||
</dl>
|
||
<p><span class="target" id="index-0"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0338"><strong>PEP 338</strong></a> – Executing modules as scripts</p>
|
||
</div>
|
||
<div class="versionchanged">
|
||
<p><span class="versionmodified changed">Changed in version 3.1: </span>Supply the package name to run a <code class="docutils literal notranslate"><span class="pre">__main__</span></code> submodule.</p>
|
||
</div>
|
||
<div class="versionchanged">
|
||
<p><span class="versionmodified changed">Changed in version 3.4: </span>namespace packages are also supported</p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="describe">
|
||
<dt>
|
||
<code class="descname">-</code></dt>
|
||
<dd><p>Read commands from standard input (<a class="reference internal" href="../library/sys.html#sys.stdin" title="sys.stdin"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.stdin</span></code></a>). If standard input is
|
||
a terminal, <a class="reference internal" href="#cmdoption-i"><code class="xref std std-option docutils literal notranslate"><span class="pre">-i</span></code></a> is implied.</p>
|
||
<p>If this option is given, the first element of <a class="reference internal" href="../library/sys.html#sys.argv" title="sys.argv"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.argv</span></code></a> will be
|
||
<code class="docutils literal notranslate"><span class="pre">"-"</span></code> and the current directory will be added to the start of
|
||
<a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a>.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="describe">
|
||
<dt>
|
||
<code class="descname"><script></code></dt>
|
||
<dd><p>Execute the Python code contained in <em>script</em>, which must be a filesystem
|
||
path (absolute or relative) referring to either a Python file, a directory
|
||
containing a <code class="docutils literal notranslate"><span class="pre">__main__.py</span></code> file, or a zipfile containing a
|
||
<code class="docutils literal notranslate"><span class="pre">__main__.py</span></code> file.</p>
|
||
<p>If this option is given, the first element of <a class="reference internal" href="../library/sys.html#sys.argv" title="sys.argv"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.argv</span></code></a> will be the
|
||
script name as given on the command line.</p>
|
||
<p>If the script name refers directly to a Python file, the directory
|
||
containing that file is added to the start of <a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a>, and the
|
||
file is executed as the <a class="reference internal" href="../library/__main__.html#module-__main__" title="__main__: The environment where the top-level script is run."><code class="xref py py-mod docutils literal notranslate"><span class="pre">__main__</span></code></a> module.</p>
|
||
<p>If the script name refers to a directory or zipfile, the script name is
|
||
added to the start of <a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a> and the <code class="docutils literal notranslate"><span class="pre">__main__.py</span></code> file in
|
||
that location is executed as the <a class="reference internal" href="../library/__main__.html#module-__main__" title="__main__: The environment where the top-level script is run."><code class="xref py py-mod docutils literal notranslate"><span class="pre">__main__</span></code></a> module.</p>
|
||
<div class="admonition seealso">
|
||
<p class="admonition-title">See also</p>
|
||
<dl class="simple">
|
||
<dt><a class="reference internal" href="../library/runpy.html#runpy.run_path" title="runpy.run_path"><code class="xref py py-func docutils literal notranslate"><span class="pre">runpy.run_path()</span></code></a></dt><dd><p>Equivalent functionality directly available to Python code</p>
|
||
</dd>
|
||
</dl>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<p>If no interface option is given, <a class="reference internal" href="#cmdoption-i"><code class="xref std std-option docutils literal notranslate"><span class="pre">-i</span></code></a> is implied, <code class="docutils literal notranslate"><span class="pre">sys.argv[0]</span></code> is
|
||
an empty string (<code class="docutils literal notranslate"><span class="pre">""</span></code>) and the current directory will be added to the
|
||
start of <a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a>. Also, tab-completion and history editing is
|
||
automatically enabled, if available on your platform (see
|
||
<a class="reference internal" href="../library/site.html#rlcompleter-config"><span class="std std-ref">Readline configuration</span></a>).</p>
|
||
<div class="admonition seealso">
|
||
<p class="admonition-title">See also</p>
|
||
<p><a class="reference internal" href="../tutorial/interpreter.html#tut-invoking"><span class="std std-ref">Invoking the Interpreter</span></a></p>
|
||
</div>
|
||
<div class="versionchanged">
|
||
<p><span class="versionmodified changed">Changed in version 3.4: </span>Automatic enabling of tab-completion and history editing.</p>
|
||
</div>
|
||
</div>
|
||
<div class="section" id="generic-options">
|
||
<h3>1.1.2. Generic options<a class="headerlink" href="#generic-options" title="Permalink to this headline">¶</a></h3>
|
||
<dl class="cmdoption">
|
||
<dt id="cmdoption">
|
||
<code class="descname">-?</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption" title="Permalink to this definition">¶</a></dt>
|
||
<dt id="cmdoption-h">
|
||
<code class="descname">-h</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-h" title="Permalink to this definition">¶</a></dt>
|
||
<dt id="cmdoption-help">
|
||
<code class="descname">--help</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-help" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Print a short description of all command line options.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="cmdoption">
|
||
<dt id="cmdoption-v">
|
||
<code class="descname">-V</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-v" title="Permalink to this definition">¶</a></dt>
|
||
<dt id="cmdoption-version">
|
||
<code class="descname">--version</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-version" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Print the Python version number and exit. Example output could be:</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>Python 3.7.0b2+
|
||
</pre></div>
|
||
</div>
|
||
<p>When given twice, print more information about the build, like:</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>Python 3.7.0b2+ (3.7:0c076caaa8, Sep 22 2018, 12:04:24)
|
||
[GCC 6.2.0 20161005]
|
||
</pre></div>
|
||
</div>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.6: </span>The <code class="docutils literal notranslate"><span class="pre">-VV</span></code> option.</p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
</div>
|
||
<div class="section" id="miscellaneous-options">
|
||
<span id="using-on-misc-options"></span><h3>1.1.3. Miscellaneous options<a class="headerlink" href="#miscellaneous-options" title="Permalink to this headline">¶</a></h3>
|
||
<dl class="cmdoption">
|
||
<dt id="cmdoption-b">
|
||
<code class="descname">-b</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-b" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Issue a warning when comparing <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> or <a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a> with
|
||
<a class="reference internal" href="../library/stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a> or <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> with <a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate"><span class="pre">int</span></code></a>. Issue an error when the
|
||
option is given twice (<code class="xref std std-option docutils literal notranslate"><span class="pre">-bb</span></code>).</p>
|
||
<div class="versionchanged">
|
||
<p><span class="versionmodified changed">Changed in version 3.5: </span>Affects comparisons of <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> with <a class="reference internal" href="../library/functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate"><span class="pre">int</span></code></a>.</p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="cmdoption">
|
||
<dt id="id1">
|
||
<code class="descname">-B</code><code class="descclassname"></code><a class="headerlink" href="#id1" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If given, Python won’t try to write <code class="docutils literal notranslate"><span class="pre">.pyc</span></code> files on the
|
||
import of source modules. See also <span class="target" id="index-1"></span><a class="reference internal" href="#envvar-PYTHONDONTWRITEBYTECODE"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONDONTWRITEBYTECODE</span></code></a>.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="cmdoption">
|
||
<dt id="cmdoption-check-hash-based-pycs">
|
||
<code class="descname">--check-hash-based-pycs</code><code class="descclassname"> default|always|never</code><a class="headerlink" href="#cmdoption-check-hash-based-pycs" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Control the validation behavior of hash-based <code class="docutils literal notranslate"><span class="pre">.pyc</span></code> files. See
|
||
<a class="reference internal" href="../reference/import.html#pyc-invalidation"><span class="std std-ref">Cached bytecode invalidation</span></a>. When set to <code class="docutils literal notranslate"><span class="pre">default</span></code>, checked and unchecked
|
||
hash-based bytecode cache files are validated according to their default
|
||
semantics. When set to <code class="docutils literal notranslate"><span class="pre">always</span></code>, all hash-based <code class="docutils literal notranslate"><span class="pre">.pyc</span></code> files, whether
|
||
checked or unchecked, are validated against their corresponding source
|
||
file. When set to <code class="docutils literal notranslate"><span class="pre">never</span></code>, hash-based <code class="docutils literal notranslate"><span class="pre">.pyc</span></code> files are not validated
|
||
against their corresponding source files.</p>
|
||
<p>The semantics of timestamp-based <code class="docutils literal notranslate"><span class="pre">.pyc</span></code> files are unaffected by this
|
||
option.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="cmdoption">
|
||
<dt id="cmdoption-d">
|
||
<code class="descname">-d</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-d" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Turn on parser debugging output (for expert only, depending on compilation
|
||
options). See also <span class="target" id="index-2"></span><a class="reference internal" href="#envvar-PYTHONDEBUG"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONDEBUG</span></code></a>.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="cmdoption">
|
||
<dt id="cmdoption-e">
|
||
<code class="descname">-E</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-e" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Ignore all <span class="target" id="index-3"></span><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHON*</span></code> environment variables, e.g.
|
||
<span class="target" id="index-4"></span><a class="reference internal" href="#envvar-PYTHONPATH"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONPATH</span></code></a> and <span class="target" id="index-5"></span><a class="reference internal" href="#envvar-PYTHONHOME"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONHOME</span></code></a>, that might be set.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="cmdoption">
|
||
<dt id="cmdoption-i">
|
||
<code class="descname">-i</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-i" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>When a script is passed as first argument or the <a class="reference internal" href="#cmdoption-c"><code class="xref std std-option docutils literal notranslate"><span class="pre">-c</span></code></a> option is used,
|
||
enter interactive mode after executing the script or the command, even when
|
||
<a class="reference internal" href="../library/sys.html#sys.stdin" title="sys.stdin"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.stdin</span></code></a> does not appear to be a terminal. The
|
||
<span class="target" id="index-6"></span><a class="reference internal" href="#envvar-PYTHONSTARTUP"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONSTARTUP</span></code></a> file is not read.</p>
|
||
<p>This can be useful to inspect global variables or a stack trace when a script
|
||
raises an exception. See also <span class="target" id="index-7"></span><a class="reference internal" href="#envvar-PYTHONINSPECT"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONINSPECT</span></code></a>.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="cmdoption">
|
||
<dt id="id2">
|
||
<code class="descname">-I</code><code class="descclassname"></code><a class="headerlink" href="#id2" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Run Python in isolated mode. This also implies -E and -s.
|
||
In isolated mode <a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a> contains neither the script’s directory nor
|
||
the user’s site-packages directory. All <span class="target" id="index-8"></span><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHON*</span></code> environment
|
||
variables are ignored, too. Further restrictions may be imposed to prevent
|
||
the user from injecting malicious code.</p>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.4.</span></p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="cmdoption">
|
||
<dt id="cmdoption-o">
|
||
<code class="descname">-O</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-o" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Remove assert statements and any code conditional on the value of
|
||
<a class="reference internal" href="../library/constants.html#__debug__" title="__debug__"><code class="xref py py-const docutils literal notranslate"><span class="pre">__debug__</span></code></a>. Augment the filename for compiled
|
||
(<a class="reference internal" href="../glossary.html#term-bytecode"><span class="xref std std-term">bytecode</span></a>) files by adding <code class="docutils literal notranslate"><span class="pre">.opt-1</span></code> before the <code class="docutils literal notranslate"><span class="pre">.pyc</span></code>
|
||
extension (see <span class="target" id="index-9"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0488"><strong>PEP 488</strong></a>). See also <span class="target" id="index-10"></span><a class="reference internal" href="#envvar-PYTHONOPTIMIZE"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONOPTIMIZE</span></code></a>.</p>
|
||
<div class="versionchanged">
|
||
<p><span class="versionmodified changed">Changed in version 3.5: </span>Modify <code class="docutils literal notranslate"><span class="pre">.pyc</span></code> filenames according to <span class="target" id="index-11"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0488"><strong>PEP 488</strong></a>.</p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="cmdoption">
|
||
<dt id="cmdoption-oo">
|
||
<code class="descname">-OO</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-oo" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Do <a class="reference internal" href="#cmdoption-o"><code class="xref std std-option docutils literal notranslate"><span class="pre">-O</span></code></a> and also discard docstrings. Augment the filename
|
||
for compiled (<a class="reference internal" href="../glossary.html#term-bytecode"><span class="xref std std-term">bytecode</span></a>) files by adding <code class="docutils literal notranslate"><span class="pre">.opt-2</span></code> before the
|
||
<code class="docutils literal notranslate"><span class="pre">.pyc</span></code> extension (see <span class="target" id="index-12"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0488"><strong>PEP 488</strong></a>).</p>
|
||
<div class="versionchanged">
|
||
<p><span class="versionmodified changed">Changed in version 3.5: </span>Modify <code class="docutils literal notranslate"><span class="pre">.pyc</span></code> filenames according to <span class="target" id="index-13"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0488"><strong>PEP 488</strong></a>.</p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="cmdoption">
|
||
<dt id="cmdoption-q">
|
||
<code class="descname">-q</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-q" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Don’t display the copyright and version messages even in interactive mode.</p>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.2.</span></p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="cmdoption">
|
||
<dt id="cmdoption-r">
|
||
<code class="descname">-R</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-r" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Turn on hash randomization. This option only has an effect if the
|
||
<span class="target" id="index-14"></span><a class="reference internal" href="#envvar-PYTHONHASHSEED"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONHASHSEED</span></code></a> environment variable is set to <code class="docutils literal notranslate"><span class="pre">0</span></code>, since hash
|
||
randomization is enabled by default.</p>
|
||
<p>On previous versions of Python, this option turns on hash randomization,
|
||
so that the <a class="reference internal" href="../reference/datamodel.html#object.__hash__" title="object.__hash__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__hash__()</span></code></a> values of str, bytes and datetime
|
||
are “salted” with an unpredictable random value. Although they remain
|
||
constant within an individual Python process, they are not predictable
|
||
between repeated invocations of Python.</p>
|
||
<p>Hash randomization is intended to provide protection against a
|
||
denial-of-service caused by carefully-chosen inputs that exploit the worst
|
||
case performance of a dict construction, O(n^2) complexity. See
|
||
<a class="reference external" href="http://www.ocert.org/advisories/ocert-2011-003.html">http://www.ocert.org/advisories/ocert-2011-003.html</a> for details.</p>
|
||
<p><span class="target" id="index-15"></span><a class="reference internal" href="#envvar-PYTHONHASHSEED"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONHASHSEED</span></code></a> allows you to set a fixed value for the hash
|
||
seed secret.</p>
|
||
<div class="versionchanged">
|
||
<p><span class="versionmodified changed">Changed in version 3.7: </span>The option is no longer ignored.</p>
|
||
</div>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.2.3.</span></p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="cmdoption">
|
||
<dt id="cmdoption-s">
|
||
<code class="descname">-s</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-s" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Don’t add the <a class="reference internal" href="../library/site.html#site.USER_SITE" title="site.USER_SITE"><code class="xref py py-data docutils literal notranslate"><span class="pre">user</span> <span class="pre">site-packages</span> <span class="pre">directory</span></code></a> to
|
||
<a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a>.</p>
|
||
<div class="admonition seealso">
|
||
<p class="admonition-title">See also</p>
|
||
<p><span class="target" id="index-16"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0370"><strong>PEP 370</strong></a> – Per user site-packages directory</p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="cmdoption">
|
||
<dt id="id3">
|
||
<code class="descname">-S</code><code class="descclassname"></code><a class="headerlink" href="#id3" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Disable the import of the module <a class="reference internal" href="../library/site.html#module-site" title="site: Module responsible for site-specific configuration."><code class="xref py py-mod docutils literal notranslate"><span class="pre">site</span></code></a> and the site-dependent
|
||
manipulations of <a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a> that it entails. Also disable these
|
||
manipulations if <a class="reference internal" href="../library/site.html#module-site" title="site: Module responsible for site-specific configuration."><code class="xref py py-mod docutils literal notranslate"><span class="pre">site</span></code></a> is explicitly imported later (call
|
||
<a class="reference internal" href="../library/site.html#site.main" title="site.main"><code class="xref py py-func docutils literal notranslate"><span class="pre">site.main()</span></code></a> if you want them to be triggered).</p>
|
||
</dd></dl>
|
||
|
||
<dl class="cmdoption">
|
||
<dt id="cmdoption-u">
|
||
<code class="descname">-u</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-u" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Force the stdout and stderr streams to be unbuffered. This option has no
|
||
effect on the stdin stream.</p>
|
||
<p>See also <span class="target" id="index-17"></span><a class="reference internal" href="#envvar-PYTHONUNBUFFERED"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONUNBUFFERED</span></code></a>.</p>
|
||
<div class="versionchanged">
|
||
<p><span class="versionmodified changed">Changed in version 3.7: </span>The text layer of the stdout and stderr streams now is unbuffered.</p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="cmdoption">
|
||
<dt id="id4">
|
||
<code class="descname">-v</code><code class="descclassname"></code><a class="headerlink" href="#id4" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Print a message each time a module is initialized, showing the place
|
||
(filename or built-in module) from which it is loaded. When given twice
|
||
(<code class="xref std std-option docutils literal notranslate"><span class="pre">-vv</span></code>), print a message for each file that is checked for when
|
||
searching for a module. Also provides information on module cleanup at exit.
|
||
See also <span class="target" id="index-18"></span><a class="reference internal" href="#envvar-PYTHONVERBOSE"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONVERBOSE</span></code></a>.</p>
|
||
</dd></dl>
|
||
|
||
<span class="target" id="using-on-warnings"></span><dl class="cmdoption">
|
||
<dt id="cmdoption-w">
|
||
<code class="descname">-W</code><code class="descclassname"> arg</code><a class="headerlink" href="#cmdoption-w" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Warning control. Python’s warning machinery by default prints warning
|
||
messages to <a class="reference internal" href="../library/sys.html#sys.stderr" title="sys.stderr"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.stderr</span></code></a>. A typical warning message has the following
|
||
form:</p>
|
||
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>file:line: category: message
|
||
</pre></div>
|
||
</div>
|
||
<p>By default, each warning is printed once for each source line where it
|
||
occurs. This option controls how often warnings are printed.</p>
|
||
<p>Multiple <a class="reference internal" href="#cmdoption-w"><code class="xref std std-option docutils literal notranslate"><span class="pre">-W</span></code></a> options may be given; when a warning matches more than
|
||
one option, the action for the last matching option is performed. Invalid
|
||
<a class="reference internal" href="#cmdoption-w"><code class="xref std std-option docutils literal notranslate"><span class="pre">-W</span></code></a> options are ignored (though, a warning message is printed about
|
||
invalid options when the first warning is issued).</p>
|
||
<p>Warnings can also be controlled using the <span class="target" id="index-19"></span><a class="reference internal" href="#envvar-PYTHONWARNINGS"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONWARNINGS</span></code></a>
|
||
environment variable and from within a Python program using the
|
||
<a class="reference internal" href="../library/warnings.html#module-warnings" title="warnings: Issue warning messages and control their disposition."><code class="xref py py-mod docutils literal notranslate"><span class="pre">warnings</span></code></a> module.</p>
|
||
<p>The simplest settings apply a particular action unconditionally to all
|
||
warnings emitted by a process (even those that are otherwise ignored by
|
||
default):</p>
|
||
<div class="highlight-sh notranslate"><div class="highlight"><pre><span></span>-Wdefault <span class="c1"># Warn once per call location</span>
|
||
-Werror <span class="c1"># Convert to exceptions</span>
|
||
-Walways <span class="c1"># Warn every time</span>
|
||
-Wmodule <span class="c1"># Warn once per calling module</span>
|
||
-Wonce <span class="c1"># Warn once per Python process</span>
|
||
-Wignore <span class="c1"># Never warn</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>The action names can be abbreviated as desired (e.g. <code class="docutils literal notranslate"><span class="pre">-Wi</span></code>, <code class="docutils literal notranslate"><span class="pre">-Wd</span></code>,
|
||
<code class="docutils literal notranslate"><span class="pre">-Wa</span></code>, <code class="docutils literal notranslate"><span class="pre">-We</span></code>) and the interpreter will resolve them to the appropriate
|
||
action name.</p>
|
||
<p>See <a class="reference internal" href="../library/warnings.html#warning-filter"><span class="std std-ref">The Warnings Filter</span></a> and <a class="reference internal" href="../library/warnings.html#describing-warning-filters"><span class="std std-ref">Describing Warning Filters</span></a> for more
|
||
details.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="cmdoption">
|
||
<dt id="cmdoption-x">
|
||
<code class="descname">-x</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-x" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Skip the first line of the source, allowing use of non-Unix forms of
|
||
<code class="docutils literal notranslate"><span class="pre">#!cmd</span></code>. This is intended for a DOS specific hack only.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="cmdoption">
|
||
<dt id="id5">
|
||
<code class="descname">-X</code><code class="descclassname"></code><a class="headerlink" href="#id5" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Reserved for various implementation-specific options. CPython currently
|
||
defines the following possible values:</p>
|
||
<ul class="simple">
|
||
<li><p><code class="docutils literal notranslate"><span class="pre">-X</span> <span class="pre">faulthandler</span></code> to enable <a class="reference internal" href="../library/faulthandler.html#module-faulthandler" title="faulthandler: Dump the Python traceback."><code class="xref py py-mod docutils literal notranslate"><span class="pre">faulthandler</span></code></a>;</p></li>
|
||
<li><p><code class="docutils literal notranslate"><span class="pre">-X</span> <span class="pre">showrefcount</span></code> to output the total reference count and number of used
|
||
memory blocks when the program finishes or after each statement in the
|
||
interactive interpreter. This only works on debug builds.</p></li>
|
||
<li><p><code class="docutils literal notranslate"><span class="pre">-X</span> <span class="pre">tracemalloc</span></code> to start tracing Python memory allocations using the
|
||
<a class="reference internal" href="../library/tracemalloc.html#module-tracemalloc" title="tracemalloc: Trace memory allocations."><code class="xref py py-mod docutils literal notranslate"><span class="pre">tracemalloc</span></code></a> module. By default, only the most recent frame is
|
||
stored in a traceback of a trace. Use <code class="docutils literal notranslate"><span class="pre">-X</span> <span class="pre">tracemalloc=NFRAME</span></code> to start
|
||
tracing with a traceback limit of <em>NFRAME</em> frames. See the
|
||
<a class="reference internal" href="../library/tracemalloc.html#tracemalloc.start" title="tracemalloc.start"><code class="xref py py-func docutils literal notranslate"><span class="pre">tracemalloc.start()</span></code></a> for more information.</p></li>
|
||
<li><p><code class="docutils literal notranslate"><span class="pre">-X</span> <span class="pre">showalloccount</span></code> to output the total count of allocated objects for
|
||
each type when the program finishes. This only works when Python was built with
|
||
<code class="docutils literal notranslate"><span class="pre">COUNT_ALLOCS</span></code> defined.</p></li>
|
||
<li><p><code class="docutils literal notranslate"><span class="pre">-X</span> <span class="pre">importtime</span></code> to show how long each import takes. It shows module
|
||
name, cumulative time (including nested imports) and self time (excluding
|
||
nested imports). Note that its output may be broken in multi-threaded
|
||
application. Typical usage is <code class="docutils literal notranslate"><span class="pre">python3</span> <span class="pre">-X</span> <span class="pre">importtime</span> <span class="pre">-c</span> <span class="pre">'import</span>
|
||
<span class="pre">asyncio'</span></code>. See also <span class="target" id="index-20"></span><a class="reference internal" href="#envvar-PYTHONPROFILEIMPORTTIME"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONPROFILEIMPORTTIME</span></code></a>.</p></li>
|
||
<li><p><code class="docutils literal notranslate"><span class="pre">-X</span> <span class="pre">dev</span></code>: enable CPython’s “development mode”, introducing additional
|
||
runtime checks which are too expensive to be enabled by default. It should
|
||
not be more verbose than the default if the code is correct: new warnings
|
||
are only emitted when an issue is detected. Effect of the developer mode:</p>
|
||
<ul>
|
||
<li><p>Add <code class="docutils literal notranslate"><span class="pre">default</span></code> warning filter, as <a class="reference internal" href="#cmdoption-w"><code class="xref std std-option docutils literal notranslate"><span class="pre">-W</span></code></a> <code class="docutils literal notranslate"><span class="pre">default</span></code>.</p></li>
|
||
<li><p>Install debug hooks on memory allocators: see the
|
||
<a class="reference internal" href="../c-api/memory.html#c.PyMem_SetupDebugHooks" title="PyMem_SetupDebugHooks"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyMem_SetupDebugHooks()</span></code></a> C function.</p></li>
|
||
<li><p>Enable the <a class="reference internal" href="../library/faulthandler.html#module-faulthandler" title="faulthandler: Dump the Python traceback."><code class="xref py py-mod docutils literal notranslate"><span class="pre">faulthandler</span></code></a> module to dump the Python traceback
|
||
on a crash.</p></li>
|
||
<li><p>Enable <a class="reference internal" href="../library/asyncio-dev.html#asyncio-debug-mode"><span class="std std-ref">asyncio debug mode</span></a>.</p></li>
|
||
<li><p>Set the <code class="xref py py-attr docutils literal notranslate"><span class="pre">dev_mode</span></code> attribute of <a class="reference internal" href="../library/sys.html#sys.flags" title="sys.flags"><code class="xref py py-attr docutils literal notranslate"><span class="pre">sys.flags</span></code></a> to
|
||
<code class="docutils literal notranslate"><span class="pre">True</span></code></p></li>
|
||
</ul>
|
||
</li>
|
||
<li><p><code class="docutils literal notranslate"><span class="pre">-X</span> <span class="pre">utf8</span></code> enables UTF-8 mode for operating system interfaces, overriding
|
||
the default locale-aware mode. <code class="docutils literal notranslate"><span class="pre">-X</span> <span class="pre">utf8=0</span></code> explicitly disables UTF-8
|
||
mode (even when it would otherwise activate automatically).
|
||
See <span class="target" id="index-21"></span><a class="reference internal" href="#envvar-PYTHONUTF8"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONUTF8</span></code></a> for more details.</p></li>
|
||
</ul>
|
||
<p>It also allows passing arbitrary values and retrieving them through the
|
||
<a class="reference internal" href="../library/sys.html#sys._xoptions" title="sys._xoptions"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys._xoptions</span></code></a> dictionary.</p>
|
||
<div class="versionchanged">
|
||
<p><span class="versionmodified changed">Changed in version 3.2: </span>The <a class="reference internal" href="#id5"><code class="xref std std-option docutils literal notranslate"><span class="pre">-X</span></code></a> option was added.</p>
|
||
</div>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.3: </span>The <code class="docutils literal notranslate"><span class="pre">-X</span> <span class="pre">faulthandler</span></code> option.</p>
|
||
</div>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.4: </span>The <code class="docutils literal notranslate"><span class="pre">-X</span> <span class="pre">showrefcount</span></code> and <code class="docutils literal notranslate"><span class="pre">-X</span> <span class="pre">tracemalloc</span></code> options.</p>
|
||
</div>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.6: </span>The <code class="docutils literal notranslate"><span class="pre">-X</span> <span class="pre">showalloccount</span></code> option.</p>
|
||
</div>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.7: </span>The <code class="docutils literal notranslate"><span class="pre">-X</span> <span class="pre">importtime</span></code>, <code class="docutils literal notranslate"><span class="pre">-X</span> <span class="pre">dev</span></code> and <code class="docutils literal notranslate"><span class="pre">-X</span> <span class="pre">utf8</span></code> options.</p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
</div>
|
||
<div class="section" id="options-you-shouldn-t-use">
|
||
<h3>1.1.4. Options you shouldn’t use<a class="headerlink" href="#options-you-shouldn-t-use" title="Permalink to this headline">¶</a></h3>
|
||
<dl class="cmdoption">
|
||
<dt id="cmdoption-j">
|
||
<code class="descname">-J</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-j" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Reserved for use by <a class="reference external" href="http://www.jython.org/">Jython</a>.</p>
|
||
</dd></dl>
|
||
|
||
</div>
|
||
</div>
|
||
<div class="section" id="environment-variables">
|
||
<span id="using-on-envvars"></span><h2>1.2. Environment variables<a class="headerlink" href="#environment-variables" title="Permalink to this headline">¶</a></h2>
|
||
<p>These environment variables influence Python’s behavior, they are processed
|
||
before the command-line switches other than -E or -I. It is customary that
|
||
command-line switches override environmental variables where there is a
|
||
conflict.</p>
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONHOME">
|
||
<code class="descname">PYTHONHOME</code><a class="headerlink" href="#envvar-PYTHONHOME" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Change the location of the standard Python libraries. By default, the
|
||
libraries are searched in <code class="file docutils literal notranslate"><em><span class="pre">prefix</span></em><span class="pre">/lib/python</span><em><span class="pre">version</span></em></code> and
|
||
<code class="file docutils literal notranslate"><em><span class="pre">exec_prefix</span></em><span class="pre">/lib/python</span><em><span class="pre">version</span></em></code>, where <code class="file docutils literal notranslate"><em><span class="pre">prefix</span></em></code> and
|
||
<code class="file docutils literal notranslate"><em><span class="pre">exec_prefix</span></em></code> are installation-dependent directories, both defaulting
|
||
to <code class="file docutils literal notranslate"><span class="pre">/usr/local</span></code>.</p>
|
||
<p>When <span class="target" id="index-22"></span><a class="reference internal" href="#envvar-PYTHONHOME"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONHOME</span></code></a> is set to a single directory, its value replaces
|
||
both <code class="file docutils literal notranslate"><em><span class="pre">prefix</span></em></code> and <code class="file docutils literal notranslate"><em><span class="pre">exec_prefix</span></em></code>. To specify different values
|
||
for these, set <span class="target" id="index-23"></span><a class="reference internal" href="#envvar-PYTHONHOME"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONHOME</span></code></a> to <code class="file docutils literal notranslate"><em><span class="pre">prefix</span></em><span class="pre">:</span><em><span class="pre">exec_prefix</span></em></code>.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONPATH">
|
||
<code class="descname">PYTHONPATH</code><a class="headerlink" href="#envvar-PYTHONPATH" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Augment the default search path for module files. The format is the same as
|
||
the shell’s <span class="target" id="index-24"></span><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PATH</span></code>: one or more directory pathnames separated by
|
||
<a class="reference internal" href="../library/os.html#os.pathsep" title="os.pathsep"><code class="xref py py-data docutils literal notranslate"><span class="pre">os.pathsep</span></code></a> (e.g. colons on Unix or semicolons on Windows).
|
||
Non-existent directories are silently ignored.</p>
|
||
<p>In addition to normal directories, individual <span class="target" id="index-25"></span><a class="reference internal" href="#envvar-PYTHONPATH"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONPATH</span></code></a> entries
|
||
may refer to zipfiles containing pure Python modules (in either source or
|
||
compiled form). Extension modules cannot be imported from zipfiles.</p>
|
||
<p>The default search path is installation dependent, but generally begins with
|
||
<code class="file docutils literal notranslate"><em><span class="pre">prefix</span></em><span class="pre">/lib/python</span><em><span class="pre">version</span></em></code> (see <span class="target" id="index-26"></span><a class="reference internal" href="#envvar-PYTHONHOME"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONHOME</span></code></a> above). It
|
||
is <em>always</em> appended to <span class="target" id="index-27"></span><a class="reference internal" href="#envvar-PYTHONPATH"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONPATH</span></code></a>.</p>
|
||
<p>An additional directory will be inserted in the search path in front of
|
||
<span class="target" id="index-28"></span><a class="reference internal" href="#envvar-PYTHONPATH"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONPATH</span></code></a> as described above under
|
||
<a class="reference internal" href="#using-on-interface-options"><span class="std std-ref">Interface options</span></a>. The search path can be manipulated from
|
||
within a Python program as the variable <a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a>.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONSTARTUP">
|
||
<code class="descname">PYTHONSTARTUP</code><a class="headerlink" href="#envvar-PYTHONSTARTUP" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If this is the name of a readable file, the Python commands in that file are
|
||
executed before the first prompt is displayed in interactive mode. The file
|
||
is executed in the same namespace where interactive commands are executed so
|
||
that objects defined or imported in it can be used without qualification in
|
||
the interactive session. You can also change the prompts <a class="reference internal" href="../library/sys.html#sys.ps1" title="sys.ps1"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.ps1</span></code></a> and
|
||
<a class="reference internal" href="../library/sys.html#sys.ps2" title="sys.ps2"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.ps2</span></code></a> and the hook <a class="reference internal" href="../library/sys.html#sys.__interactivehook__" title="sys.__interactivehook__"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.__interactivehook__</span></code></a> in this file.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONOPTIMIZE">
|
||
<code class="descname">PYTHONOPTIMIZE</code><a class="headerlink" href="#envvar-PYTHONOPTIMIZE" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If this is set to a non-empty string it is equivalent to specifying the
|
||
<a class="reference internal" href="#cmdoption-o"><code class="xref std std-option docutils literal notranslate"><span class="pre">-O</span></code></a> option. If set to an integer, it is equivalent to specifying
|
||
<a class="reference internal" href="#cmdoption-o"><code class="xref std std-option docutils literal notranslate"><span class="pre">-O</span></code></a> multiple times.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONBREAKPOINT">
|
||
<code class="descname">PYTHONBREAKPOINT</code><a class="headerlink" href="#envvar-PYTHONBREAKPOINT" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If this is set, it names a callable using dotted-path notation. The module
|
||
containing the callable will be imported and then the callable will be run
|
||
by the default implementation of <a class="reference internal" href="../library/sys.html#sys.breakpointhook" title="sys.breakpointhook"><code class="xref py py-func docutils literal notranslate"><span class="pre">sys.breakpointhook()</span></code></a> which itself is
|
||
called by built-in <a class="reference internal" href="../library/functions.html#breakpoint" title="breakpoint"><code class="xref py py-func docutils literal notranslate"><span class="pre">breakpoint()</span></code></a>. If not set, or set to the empty
|
||
string, it is equivalent to the value “pdb.set_trace”. Setting this to the
|
||
string “0” causes the default implementation of <a class="reference internal" href="../library/sys.html#sys.breakpointhook" title="sys.breakpointhook"><code class="xref py py-func docutils literal notranslate"><span class="pre">sys.breakpointhook()</span></code></a>
|
||
to do nothing but return immediately.</p>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.7.</span></p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONDEBUG">
|
||
<code class="descname">PYTHONDEBUG</code><a class="headerlink" href="#envvar-PYTHONDEBUG" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If this is set to a non-empty string it is equivalent to specifying the
|
||
<a class="reference internal" href="#cmdoption-d"><code class="xref std std-option docutils literal notranslate"><span class="pre">-d</span></code></a> option. If set to an integer, it is equivalent to specifying
|
||
<a class="reference internal" href="#cmdoption-d"><code class="xref std std-option docutils literal notranslate"><span class="pre">-d</span></code></a> multiple times.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONINSPECT">
|
||
<code class="descname">PYTHONINSPECT</code><a class="headerlink" href="#envvar-PYTHONINSPECT" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If this is set to a non-empty string it is equivalent to specifying the
|
||
<a class="reference internal" href="#cmdoption-i"><code class="xref std std-option docutils literal notranslate"><span class="pre">-i</span></code></a> option.</p>
|
||
<p>This variable can also be modified by Python code using <a class="reference internal" href="../library/os.html#os.environ" title="os.environ"><code class="xref py py-data docutils literal notranslate"><span class="pre">os.environ</span></code></a>
|
||
to force inspect mode on program termination.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONUNBUFFERED">
|
||
<code class="descname">PYTHONUNBUFFERED</code><a class="headerlink" href="#envvar-PYTHONUNBUFFERED" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If this is set to a non-empty string it is equivalent to specifying the
|
||
<a class="reference internal" href="#cmdoption-u"><code class="xref std std-option docutils literal notranslate"><span class="pre">-u</span></code></a> option.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONVERBOSE">
|
||
<code class="descname">PYTHONVERBOSE</code><a class="headerlink" href="#envvar-PYTHONVERBOSE" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If this is set to a non-empty string it is equivalent to specifying the
|
||
<a class="reference internal" href="#id4"><code class="xref std std-option docutils literal notranslate"><span class="pre">-v</span></code></a> option. If set to an integer, it is equivalent to specifying
|
||
<a class="reference internal" href="#id4"><code class="xref std std-option docutils literal notranslate"><span class="pre">-v</span></code></a> multiple times.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONCASEOK">
|
||
<code class="descname">PYTHONCASEOK</code><a class="headerlink" href="#envvar-PYTHONCASEOK" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If this is set, Python ignores case in <a class="reference internal" href="../reference/simple_stmts.html#import"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">import</span></code></a> statements. This
|
||
only works on Windows and OS X.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONDONTWRITEBYTECODE">
|
||
<code class="descname">PYTHONDONTWRITEBYTECODE</code><a class="headerlink" href="#envvar-PYTHONDONTWRITEBYTECODE" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If this is set to a non-empty string, Python won’t try to write <code class="docutils literal notranslate"><span class="pre">.pyc</span></code>
|
||
files on the import of source modules. This is equivalent to
|
||
specifying the <a class="reference internal" href="#id1"><code class="xref std std-option docutils literal notranslate"><span class="pre">-B</span></code></a> option.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONHASHSEED">
|
||
<code class="descname">PYTHONHASHSEED</code><a class="headerlink" href="#envvar-PYTHONHASHSEED" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If this variable is not set or set to <code class="docutils literal notranslate"><span class="pre">random</span></code>, a random value is used
|
||
to seed the hashes of str, bytes and datetime objects.</p>
|
||
<p>If <span class="target" id="index-29"></span><a class="reference internal" href="#envvar-PYTHONHASHSEED"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONHASHSEED</span></code></a> is set to an integer value, it is used as a fixed
|
||
seed for generating the hash() of the types covered by the hash
|
||
randomization.</p>
|
||
<p>Its purpose is to allow repeatable hashing, such as for selftests for the
|
||
interpreter itself, or to allow a cluster of python processes to share hash
|
||
values.</p>
|
||
<p>The integer must be a decimal number in the range [0,4294967295]. Specifying
|
||
the value 0 will disable hash randomization.</p>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.2.3.</span></p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONIOENCODING">
|
||
<code class="descname">PYTHONIOENCODING</code><a class="headerlink" href="#envvar-PYTHONIOENCODING" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If this is set before running the interpreter, it overrides the encoding used
|
||
for stdin/stdout/stderr, in the syntax <code class="docutils literal notranslate"><span class="pre">encodingname:errorhandler</span></code>. Both
|
||
the <code class="docutils literal notranslate"><span class="pre">encodingname</span></code> and the <code class="docutils literal notranslate"><span class="pre">:errorhandler</span></code> parts are optional and have
|
||
the same meaning as in <a class="reference internal" href="../library/stdtypes.html#str.encode" title="str.encode"><code class="xref py py-func docutils literal notranslate"><span class="pre">str.encode()</span></code></a>.</p>
|
||
<p>For stderr, the <code class="docutils literal notranslate"><span class="pre">:errorhandler</span></code> part is ignored; the handler will always be
|
||
<code class="docutils literal notranslate"><span class="pre">'backslashreplace'</span></code>.</p>
|
||
<div class="versionchanged">
|
||
<p><span class="versionmodified changed">Changed in version 3.4: </span>The <code class="docutils literal notranslate"><span class="pre">encodingname</span></code> part is now optional.</p>
|
||
</div>
|
||
<div class="versionchanged">
|
||
<p><span class="versionmodified changed">Changed in version 3.6: </span>On Windows, the encoding specified by this variable is ignored for interactive
|
||
console buffers unless <span class="target" id="index-30"></span><a class="reference internal" href="#envvar-PYTHONLEGACYWINDOWSSTDIO"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONLEGACYWINDOWSSTDIO</span></code></a> is also specified.
|
||
Files and pipes redirected through the standard streams are not affected.</p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONNOUSERSITE">
|
||
<code class="descname">PYTHONNOUSERSITE</code><a class="headerlink" href="#envvar-PYTHONNOUSERSITE" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If this is set, Python won’t add the <a class="reference internal" href="../library/site.html#site.USER_SITE" title="site.USER_SITE"><code class="xref py py-data docutils literal notranslate"><span class="pre">user</span> <span class="pre">site-packages</span> <span class="pre">directory</span></code></a> to <a class="reference internal" href="../library/sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a>.</p>
|
||
<div class="admonition seealso">
|
||
<p class="admonition-title">See also</p>
|
||
<p><span class="target" id="index-31"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0370"><strong>PEP 370</strong></a> – Per user site-packages directory</p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONUSERBASE">
|
||
<code class="descname">PYTHONUSERBASE</code><a class="headerlink" href="#envvar-PYTHONUSERBASE" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Defines the <a class="reference internal" href="../library/site.html#site.USER_BASE" title="site.USER_BASE"><code class="xref py py-data docutils literal notranslate"><span class="pre">user</span> <span class="pre">base</span> <span class="pre">directory</span></code></a>, which is used to
|
||
compute the path of the <a class="reference internal" href="../library/site.html#site.USER_SITE" title="site.USER_SITE"><code class="xref py py-data docutils literal notranslate"><span class="pre">user</span> <span class="pre">site-packages</span> <span class="pre">directory</span></code></a>
|
||
and <a class="reference internal" href="../install/index.html#inst-alt-install-user"><span class="std std-ref">Distutils installation paths</span></a> for
|
||
<code class="docutils literal notranslate"><span class="pre">python</span> <span class="pre">setup.py</span> <span class="pre">install</span> <span class="pre">--user</span></code>.</p>
|
||
<div class="admonition seealso">
|
||
<p class="admonition-title">See also</p>
|
||
<p><span class="target" id="index-32"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0370"><strong>PEP 370</strong></a> – Per user site-packages directory</p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONEXECUTABLE">
|
||
<code class="descname">PYTHONEXECUTABLE</code><a class="headerlink" href="#envvar-PYTHONEXECUTABLE" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If this environment variable is set, <code class="docutils literal notranslate"><span class="pre">sys.argv[0]</span></code> will be set to its
|
||
value instead of the value got through the C runtime. Only works on
|
||
Mac OS X.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONWARNINGS">
|
||
<code class="descname">PYTHONWARNINGS</code><a class="headerlink" href="#envvar-PYTHONWARNINGS" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>This is equivalent to the <a class="reference internal" href="#cmdoption-w"><code class="xref std std-option docutils literal notranslate"><span class="pre">-W</span></code></a> option. If set to a comma
|
||
separated string, it is equivalent to specifying <a class="reference internal" href="#cmdoption-w"><code class="xref std std-option docutils literal notranslate"><span class="pre">-W</span></code></a> multiple
|
||
times, with filters later in the list taking precedence over those earlier
|
||
in the list.</p>
|
||
<p>The simplest settings apply a particular action unconditionally to all
|
||
warnings emitted by a process (even those that are otherwise ignored by
|
||
default):</p>
|
||
<div class="highlight-sh notranslate"><div class="highlight"><pre><span></span><span class="nv">PYTHONWARNINGS</span><span class="o">=</span>default <span class="c1"># Warn once per call location</span>
|
||
<span class="nv">PYTHONWARNINGS</span><span class="o">=</span>error <span class="c1"># Convert to exceptions</span>
|
||
<span class="nv">PYTHONWARNINGS</span><span class="o">=</span>always <span class="c1"># Warn every time</span>
|
||
<span class="nv">PYTHONWARNINGS</span><span class="o">=</span>module <span class="c1"># Warn once per calling module</span>
|
||
<span class="nv">PYTHONWARNINGS</span><span class="o">=</span>once <span class="c1"># Warn once per Python process</span>
|
||
<span class="nv">PYTHONWARNINGS</span><span class="o">=</span>ignore <span class="c1"># Never warn</span>
|
||
</pre></div>
|
||
</div>
|
||
<p>See <a class="reference internal" href="../library/warnings.html#warning-filter"><span class="std std-ref">The Warnings Filter</span></a> and <a class="reference internal" href="../library/warnings.html#describing-warning-filters"><span class="std std-ref">Describing Warning Filters</span></a> for more
|
||
details.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONFAULTHANDLER">
|
||
<code class="descname">PYTHONFAULTHANDLER</code><a class="headerlink" href="#envvar-PYTHONFAULTHANDLER" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If this environment variable is set to a non-empty string,
|
||
<a class="reference internal" href="../library/faulthandler.html#faulthandler.enable" title="faulthandler.enable"><code class="xref py py-func docutils literal notranslate"><span class="pre">faulthandler.enable()</span></code></a> is called at startup: install a handler for
|
||
<code class="xref py py-const docutils literal notranslate"><span class="pre">SIGSEGV</span></code>, <code class="xref py py-const docutils literal notranslate"><span class="pre">SIGFPE</span></code>, <code class="xref py py-const docutils literal notranslate"><span class="pre">SIGABRT</span></code>, <code class="xref py py-const docutils literal notranslate"><span class="pre">SIGBUS</span></code> and
|
||
<code class="xref py py-const docutils literal notranslate"><span class="pre">SIGILL</span></code> signals to dump the Python traceback. This is equivalent to
|
||
<a class="reference internal" href="#id5"><code class="xref std std-option docutils literal notranslate"><span class="pre">-X</span></code></a> <code class="docutils literal notranslate"><span class="pre">faulthandler</span></code> option.</p>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.3.</span></p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONTRACEMALLOC">
|
||
<code class="descname">PYTHONTRACEMALLOC</code><a class="headerlink" href="#envvar-PYTHONTRACEMALLOC" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If this environment variable is set to a non-empty string, start tracing
|
||
Python memory allocations using the <a class="reference internal" href="../library/tracemalloc.html#module-tracemalloc" title="tracemalloc: Trace memory allocations."><code class="xref py py-mod docutils literal notranslate"><span class="pre">tracemalloc</span></code></a> module. The value of
|
||
the variable is the maximum number of frames stored in a traceback of a
|
||
trace. For example, <code class="docutils literal notranslate"><span class="pre">PYTHONTRACEMALLOC=1</span></code> stores only the most recent
|
||
frame. See the <a class="reference internal" href="../library/tracemalloc.html#tracemalloc.start" title="tracemalloc.start"><code class="xref py py-func docutils literal notranslate"><span class="pre">tracemalloc.start()</span></code></a> for more information.</p>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.4.</span></p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONPROFILEIMPORTTIME">
|
||
<code class="descname">PYTHONPROFILEIMPORTTIME</code><a class="headerlink" href="#envvar-PYTHONPROFILEIMPORTTIME" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If this environment variable is set to a non-empty string, Python will
|
||
show how long each import takes. This is exactly equivalent to setting
|
||
<code class="docutils literal notranslate"><span class="pre">-X</span> <span class="pre">importtime</span></code> on the command line.</p>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.7.</span></p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONASYNCIODEBUG">
|
||
<code class="descname">PYTHONASYNCIODEBUG</code><a class="headerlink" href="#envvar-PYTHONASYNCIODEBUG" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If this environment variable is set to a non-empty string, enable the
|
||
<a class="reference internal" href="../library/asyncio-dev.html#asyncio-debug-mode"><span class="std std-ref">debug mode</span></a> of the <a class="reference internal" href="../library/asyncio.html#module-asyncio" title="asyncio: Asynchronous I/O."><code class="xref py py-mod docutils literal notranslate"><span class="pre">asyncio</span></code></a> module.</p>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.4.</span></p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONMALLOC">
|
||
<code class="descname">PYTHONMALLOC</code><a class="headerlink" href="#envvar-PYTHONMALLOC" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Set the Python memory allocators and/or install debug hooks.</p>
|
||
<p>Set the family of memory allocators used by Python:</p>
|
||
<ul class="simple">
|
||
<li><p><code class="docutils literal notranslate"><span class="pre">default</span></code>: use the <a class="reference internal" href="../c-api/memory.html#default-memory-allocators"><span class="std std-ref">default memory allocators</span></a>.</p></li>
|
||
<li><p><code class="docutils literal notranslate"><span class="pre">malloc</span></code>: use the <code class="xref c c-func docutils literal notranslate"><span class="pre">malloc()</span></code> function of the C library
|
||
for all domains (<a class="reference internal" href="../c-api/memory.html#c.PYMEM_DOMAIN_RAW" title="PYMEM_DOMAIN_RAW"><code class="xref c c-data docutils literal notranslate"><span class="pre">PYMEM_DOMAIN_RAW</span></code></a>, <a class="reference internal" href="../c-api/memory.html#c.PYMEM_DOMAIN_MEM" title="PYMEM_DOMAIN_MEM"><code class="xref c c-data docutils literal notranslate"><span class="pre">PYMEM_DOMAIN_MEM</span></code></a>,
|
||
<a class="reference internal" href="../c-api/memory.html#c.PYMEM_DOMAIN_OBJ" title="PYMEM_DOMAIN_OBJ"><code class="xref c c-data docutils literal notranslate"><span class="pre">PYMEM_DOMAIN_OBJ</span></code></a>).</p></li>
|
||
<li><p><code class="docutils literal notranslate"><span class="pre">pymalloc</span></code>: use the <a class="reference internal" href="../c-api/memory.html#pymalloc"><span class="std std-ref">pymalloc allocator</span></a> for
|
||
<a class="reference internal" href="../c-api/memory.html#c.PYMEM_DOMAIN_MEM" title="PYMEM_DOMAIN_MEM"><code class="xref c c-data docutils literal notranslate"><span class="pre">PYMEM_DOMAIN_MEM</span></code></a> and <a class="reference internal" href="../c-api/memory.html#c.PYMEM_DOMAIN_OBJ" title="PYMEM_DOMAIN_OBJ"><code class="xref c c-data docutils literal notranslate"><span class="pre">PYMEM_DOMAIN_OBJ</span></code></a> domains and use
|
||
the <code class="xref c c-func docutils literal notranslate"><span class="pre">malloc()</span></code> function for the <a class="reference internal" href="../c-api/memory.html#c.PYMEM_DOMAIN_RAW" title="PYMEM_DOMAIN_RAW"><code class="xref c c-data docutils literal notranslate"><span class="pre">PYMEM_DOMAIN_RAW</span></code></a> domain.</p></li>
|
||
</ul>
|
||
<p>Install debug hooks:</p>
|
||
<ul class="simple">
|
||
<li><p><code class="docutils literal notranslate"><span class="pre">debug</span></code>: install debug hooks on top of the <a class="reference internal" href="../c-api/memory.html#default-memory-allocators"><span class="std std-ref">default memory
|
||
allocators</span></a>.</p></li>
|
||
<li><p><code class="docutils literal notranslate"><span class="pre">malloc_debug</span></code>: same as <code class="docutils literal notranslate"><span class="pre">malloc</span></code> but also install debug hooks</p></li>
|
||
<li><p><code class="docutils literal notranslate"><span class="pre">pymalloc_debug</span></code>: same as <code class="docutils literal notranslate"><span class="pre">pymalloc</span></code> but also install debug hooks</p></li>
|
||
</ul>
|
||
<p>See the <a class="reference internal" href="../c-api/memory.html#default-memory-allocators"><span class="std std-ref">default memory allocators</span></a> and the
|
||
<a class="reference internal" href="../c-api/memory.html#c.PyMem_SetupDebugHooks" title="PyMem_SetupDebugHooks"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyMem_SetupDebugHooks()</span></code></a> function (install debug hooks on Python
|
||
memory allocators).</p>
|
||
<div class="versionchanged">
|
||
<p><span class="versionmodified changed">Changed in version 3.7: </span>Added the <code class="docutils literal notranslate"><span class="pre">"default"</span></code> allocator.</p>
|
||
</div>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.6.</span></p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONMALLOCSTATS">
|
||
<code class="descname">PYTHONMALLOCSTATS</code><a class="headerlink" href="#envvar-PYTHONMALLOCSTATS" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If set to a non-empty string, Python will print statistics of the
|
||
<a class="reference internal" href="../c-api/memory.html#pymalloc"><span class="std std-ref">pymalloc memory allocator</span></a> every time a new pymalloc object
|
||
arena is created, and on shutdown.</p>
|
||
<p>This variable is ignored if the <span class="target" id="index-33"></span><a class="reference internal" href="#envvar-PYTHONMALLOC"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONMALLOC</span></code></a> environment variable
|
||
is used to force the <code class="xref c c-func docutils literal notranslate"><span class="pre">malloc()</span></code> allocator of the C library, or if
|
||
Python is configured without <code class="docutils literal notranslate"><span class="pre">pymalloc</span></code> support.</p>
|
||
<div class="versionchanged">
|
||
<p><span class="versionmodified changed">Changed in version 3.6: </span>This variable can now also be used on Python compiled in release mode.
|
||
It now has no effect if set to an empty string.</p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONLEGACYWINDOWSFSENCODING">
|
||
<code class="descname">PYTHONLEGACYWINDOWSFSENCODING</code><a class="headerlink" href="#envvar-PYTHONLEGACYWINDOWSFSENCODING" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If set to a non-empty string, the default filesystem encoding and errors mode
|
||
will revert to their pre-3.6 values of ‘mbcs’ and ‘replace’, respectively.
|
||
Otherwise, the new defaults ‘utf-8’ and ‘surrogatepass’ are used.</p>
|
||
<p>This may also be enabled at runtime with
|
||
<a class="reference internal" href="../library/sys.html#sys._enablelegacywindowsfsencoding" title="sys._enablelegacywindowsfsencoding"><code class="xref py py-func docutils literal notranslate"><span class="pre">sys._enablelegacywindowsfsencoding()</span></code></a>.</p>
|
||
<p class="availability"><a class="reference internal" href="../library/intro.html#availability"><span class="std std-ref">Availability</span></a>: Windows.</p>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.6: </span>See <span class="target" id="index-34"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0529"><strong>PEP 529</strong></a> for more details.</p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONLEGACYWINDOWSSTDIO">
|
||
<code class="descname">PYTHONLEGACYWINDOWSSTDIO</code><a class="headerlink" href="#envvar-PYTHONLEGACYWINDOWSSTDIO" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If set to a non-empty string, does not use the new console reader and
|
||
writer. This means that Unicode characters will be encoded according to
|
||
the active console code page, rather than using utf-8.</p>
|
||
<p>This variable is ignored if the standard streams are redirected (to files
|
||
or pipes) rather than referring to console buffers.</p>
|
||
<p class="availability"><a class="reference internal" href="../library/intro.html#availability"><span class="std std-ref">Availability</span></a>: Windows.</p>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.6.</span></p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONCOERCECLOCALE">
|
||
<code class="descname">PYTHONCOERCECLOCALE</code><a class="headerlink" href="#envvar-PYTHONCOERCECLOCALE" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If set to the value <code class="docutils literal notranslate"><span class="pre">0</span></code>, causes the main Python command line application
|
||
to skip coercing the legacy ASCII-based C and POSIX locales to a more
|
||
capable UTF-8 based alternative.</p>
|
||
<p>If this variable is <em>not</em> set (or is set to a value other than <code class="docutils literal notranslate"><span class="pre">0</span></code>), the
|
||
<code class="docutils literal notranslate"><span class="pre">LC_ALL</span></code> locale override environment variable is also not set, and the
|
||
current locale reported for the <code class="docutils literal notranslate"><span class="pre">LC_CTYPE</span></code> category is either the default
|
||
<code class="docutils literal notranslate"><span class="pre">C</span></code> locale, or else the explicitly ASCII-based <code class="docutils literal notranslate"><span class="pre">POSIX</span></code> locale, then the
|
||
Python CLI will attempt to configure the following locales for the
|
||
<code class="docutils literal notranslate"><span class="pre">LC_CTYPE</span></code> category in the order listed before loading the interpreter
|
||
runtime:</p>
|
||
<ul class="simple">
|
||
<li><p><code class="docutils literal notranslate"><span class="pre">C.UTF-8</span></code></p></li>
|
||
<li><p><code class="docutils literal notranslate"><span class="pre">C.utf8</span></code></p></li>
|
||
<li><p><code class="docutils literal notranslate"><span class="pre">UTF-8</span></code></p></li>
|
||
</ul>
|
||
<p>If setting one of these locale categories succeeds, then the <code class="docutils literal notranslate"><span class="pre">LC_CTYPE</span></code>
|
||
environment variable will also be set accordingly in the current process
|
||
environment before the Python runtime is initialized. This ensures that in
|
||
addition to being seen by both the interpreter itself and other locale-aware
|
||
components running in the same process (such as the GNU <code class="docutils literal notranslate"><span class="pre">readline</span></code>
|
||
library), the updated setting is also seen in subprocesses (regardless of
|
||
whether or not those processes are running a Python interpreter), as well as
|
||
in operations that query the environment rather than the current C locale
|
||
(such as Python’s own <a class="reference internal" href="../library/locale.html#locale.getdefaultlocale" title="locale.getdefaultlocale"><code class="xref py py-func docutils literal notranslate"><span class="pre">locale.getdefaultlocale()</span></code></a>).</p>
|
||
<p>Configuring one of these locales (either explicitly or via the above
|
||
implicit locale coercion) automatically enables the <code class="docutils literal notranslate"><span class="pre">surrogateescape</span></code>
|
||
<a class="reference internal" href="../library/codecs.html#error-handlers"><span class="std std-ref">error handler</span></a> for <a class="reference internal" href="../library/sys.html#sys.stdin" title="sys.stdin"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.stdin</span></code></a> and
|
||
<a class="reference internal" href="../library/sys.html#sys.stdout" title="sys.stdout"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.stdout</span></code></a> (<a class="reference internal" href="../library/sys.html#sys.stderr" title="sys.stderr"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.stderr</span></code></a> continues to use <code class="docutils literal notranslate"><span class="pre">backslashreplace</span></code>
|
||
as it does in any other locale). This stream handling behavior can be
|
||
overridden using <span class="target" id="index-35"></span><a class="reference internal" href="#envvar-PYTHONIOENCODING"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONIOENCODING</span></code></a> as usual.</p>
|
||
<p>For debugging purposes, setting <code class="docutils literal notranslate"><span class="pre">PYTHONCOERCECLOCALE=warn</span></code> will cause
|
||
Python to emit warning messages on <code class="docutils literal notranslate"><span class="pre">stderr</span></code> if either the locale coercion
|
||
activates, or else if a locale that <em>would</em> have triggered coercion is
|
||
still active when the Python runtime is initialized.</p>
|
||
<p>Also note that even when locale coercion is disabled, or when it fails to
|
||
find a suitable target locale, <span class="target" id="index-36"></span><a class="reference internal" href="#envvar-PYTHONUTF8"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONUTF8</span></code></a> will still activate by
|
||
default in legacy ASCII-based locales. Both features must be disabled in
|
||
order to force the interpreter to use <code class="docutils literal notranslate"><span class="pre">ASCII</span></code> instead of <code class="docutils literal notranslate"><span class="pre">UTF-8</span></code> for
|
||
system interfaces.</p>
|
||
<p class="availability"><a class="reference internal" href="../library/intro.html#availability"><span class="std std-ref">Availability</span></a>: *nix.</p>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.7: </span>See <span class="target" id="index-37"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0538"><strong>PEP 538</strong></a> for more details.</p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONDEVMODE">
|
||
<code class="descname">PYTHONDEVMODE</code><a class="headerlink" href="#envvar-PYTHONDEVMODE" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If this environment variable is set to a non-empty string, enable the
|
||
CPython “development mode”. See the <a class="reference internal" href="#id5"><code class="xref std std-option docutils literal notranslate"><span class="pre">-X</span></code></a> <code class="docutils literal notranslate"><span class="pre">dev</span></code> option.</p>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.7.</span></p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONUTF8">
|
||
<code class="descname">PYTHONUTF8</code><a class="headerlink" href="#envvar-PYTHONUTF8" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If set to <code class="docutils literal notranslate"><span class="pre">1</span></code>, enables the interpreter’s UTF-8 mode, where <code class="docutils literal notranslate"><span class="pre">UTF-8</span></code> is
|
||
used as the text encoding for system interfaces, regardless of the
|
||
current locale setting.</p>
|
||
<p>This means that:</p>
|
||
<blockquote>
|
||
<div><ul class="simple">
|
||
<li><p><a class="reference internal" href="../library/sys.html#sys.getfilesystemencoding" title="sys.getfilesystemencoding"><code class="xref py py-func docutils literal notranslate"><span class="pre">sys.getfilesystemencoding()</span></code></a> returns <code class="docutils literal notranslate"><span class="pre">'UTF-8'</span></code> (the locale
|
||
encoding is ignored).</p></li>
|
||
<li><p><a class="reference internal" href="../library/locale.html#locale.getpreferredencoding" title="locale.getpreferredencoding"><code class="xref py py-func docutils literal notranslate"><span class="pre">locale.getpreferredencoding()</span></code></a> returns <code class="docutils literal notranslate"><span class="pre">'UTF-8'</span></code> (the locale
|
||
encoding is ignored, and the function’s <code class="docutils literal notranslate"><span class="pre">do_setlocale</span></code> parameter has no
|
||
effect).</p></li>
|
||
<li><p><a class="reference internal" href="../library/sys.html#sys.stdin" title="sys.stdin"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.stdin</span></code></a>, <a class="reference internal" href="../library/sys.html#sys.stdout" title="sys.stdout"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.stdout</span></code></a>, and <a class="reference internal" href="../library/sys.html#sys.stderr" title="sys.stderr"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.stderr</span></code></a> all use
|
||
UTF-8 as their text encoding, with the <code class="docutils literal notranslate"><span class="pre">surrogateescape</span></code>
|
||
<a class="reference internal" href="../library/codecs.html#error-handlers"><span class="std std-ref">error handler</span></a> being enabled for <a class="reference internal" href="../library/sys.html#sys.stdin" title="sys.stdin"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.stdin</span></code></a>
|
||
and <a class="reference internal" href="../library/sys.html#sys.stdout" title="sys.stdout"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.stdout</span></code></a> (<a class="reference internal" href="../library/sys.html#sys.stderr" title="sys.stderr"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.stderr</span></code></a> continues to use
|
||
<code class="docutils literal notranslate"><span class="pre">backslashreplace</span></code> as it does in the default locale-aware mode)</p></li>
|
||
</ul>
|
||
</div></blockquote>
|
||
<p>As a consequence of the changes in those lower level APIs, other higher
|
||
level APIs also exhibit different default behaviours:</p>
|
||
<blockquote>
|
||
<div><ul class="simple">
|
||
<li><p>Command line arguments, environment variables and filenames are decoded
|
||
to text using the UTF-8 encoding.</p></li>
|
||
<li><p><a class="reference internal" href="../library/os.html#os.fsdecode" title="os.fsdecode"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.fsdecode()</span></code></a> and <a class="reference internal" href="../library/os.html#os.fsencode" title="os.fsencode"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.fsencode()</span></code></a> use the UTF-8 encoding.</p></li>
|
||
<li><p><a class="reference internal" href="../library/functions.html#open" title="open"><code class="xref py py-func docutils literal notranslate"><span class="pre">open()</span></code></a>, <a class="reference internal" href="../library/io.html#io.open" title="io.open"><code class="xref py py-func docutils literal notranslate"><span class="pre">io.open()</span></code></a>, and <a class="reference internal" href="../library/codecs.html#codecs.open" title="codecs.open"><code class="xref py py-func docutils literal notranslate"><span class="pre">codecs.open()</span></code></a> use the UTF-8
|
||
encoding by default. However, they still use the strict error handler by
|
||
default so that attempting to open a binary file in text mode is likely
|
||
to raise an exception rather than producing nonsense data.</p></li>
|
||
</ul>
|
||
</div></blockquote>
|
||
<p>Note that the standard stream settings in UTF-8 mode can be overridden by
|
||
<span class="target" id="index-38"></span><a class="reference internal" href="#envvar-PYTHONIOENCODING"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONIOENCODING</span></code></a> (just as they can be in the default locale-aware
|
||
mode).</p>
|
||
<p>If set to <code class="docutils literal notranslate"><span class="pre">0</span></code>, the interpreter runs in its default locale-aware mode.</p>
|
||
<p>Setting any other non-empty string causes an error during interpreter
|
||
initialisation.</p>
|
||
<p>If this environment variable is not set at all, then the interpreter defaults
|
||
to using the current locale settings, <em>unless</em> the current locale is
|
||
identified as a legacy ASCII-based locale
|
||
(as described for <span class="target" id="index-39"></span><a class="reference internal" href="#envvar-PYTHONCOERCECLOCALE"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONCOERCECLOCALE</span></code></a>), and locale coercion is
|
||
either disabled or fails. In such legacy locales, the interpreter will
|
||
default to enabling UTF-8 mode unless explicitly instructed not to do so.</p>
|
||
<p>Also available as the <a class="reference internal" href="#id5"><code class="xref std std-option docutils literal notranslate"><span class="pre">-X</span></code></a> <code class="docutils literal notranslate"><span class="pre">utf8</span></code> option.</p>
|
||
<p class="availability"><a class="reference internal" href="../library/intro.html#availability"><span class="std std-ref">Availability</span></a>: *nix.</p>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.7: </span>See <span class="target" id="index-40"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0540"><strong>PEP 540</strong></a> for more details.</p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<div class="section" id="debug-mode-variables">
|
||
<h3>1.2.1. Debug-mode variables<a class="headerlink" href="#debug-mode-variables" title="Permalink to this headline">¶</a></h3>
|
||
<p>Setting these variables only has an effect in a debug build of Python, that is,
|
||
if Python was configured with the <code class="docutils literal notranslate"><span class="pre">--with-pydebug</span></code> build option.</p>
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONTHREADDEBUG">
|
||
<code class="descname">PYTHONTHREADDEBUG</code><a class="headerlink" href="#envvar-PYTHONTHREADDEBUG" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If set, Python will print threading debug info.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="envvar">
|
||
<dt id="envvar-PYTHONDUMPREFS">
|
||
<code class="descname">PYTHONDUMPREFS</code><a class="headerlink" href="#envvar-PYTHONDUMPREFS" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>If set, Python will dump objects and reference counts still alive after
|
||
shutting down the interpreter.</p>
|
||
</dd></dl>
|
||
|
||
</div>
|
||
</div>
|
||
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|
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<h3><a href="../contents.html">Table of Contents</a></h3>
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|
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<li><a class="reference internal" href="#">1. Command line and environment</a><ul>
|
||
<li><a class="reference internal" href="#command-line">1.1. Command line</a><ul>
|
||
<li><a class="reference internal" href="#interface-options">1.1.1. Interface options</a></li>
|
||
<li><a class="reference internal" href="#generic-options">1.1.2. Generic options</a></li>
|
||
<li><a class="reference internal" href="#miscellaneous-options">1.1.3. Miscellaneous options</a></li>
|
||
<li><a class="reference internal" href="#options-you-shouldn-t-use">1.1.4. Options you shouldn’t use</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a class="reference internal" href="#environment-variables">1.2. Environment variables</a><ul>
|
||
<li><a class="reference internal" href="#debug-mode-variables">1.2.1. Debug-mode variables</a></li>
|
||
</ul>
|
||
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|
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