add files

python-3.7.4-docs-html/_sources/tutorial/interpreter.rst.txt

@@ -0,0 +1,162 @@
+.. _tut-using:
+
+****************************
+Using the Python Interpreter
+****************************
+
+
+.. _tut-invoking:
+
+Invoking the Interpreter
+========================
+
+The Python interpreter is usually installed as :file:`/usr/local/bin/python3.7`
+on those machines where it is available; putting :file:`/usr/local/bin` in your
+Unix shell's search path makes it possible to start it by typing the command:
+
+.. code-block:: text
+
+   python3.7
+
+to the shell. [#]_ Since the choice of the directory where the interpreter lives
+is an installation option, other places are possible; check with your local
+Python guru or system administrator.  (E.g., :file:`/usr/local/python` is a
+popular alternative location.)
+
+On Windows machines where you have installed from the :ref:`Microsoft Store
+<windows-store>`, the :file:`python3.7` command will be available. If you have
+the :ref:`py.exe launcher <launcher>` installed, you can use the :file:`py`
+command. See :ref:`setting-envvars` for other ways to launch Python.
+
+Typing an end-of-file character (:kbd:`Control-D` on Unix, :kbd:`Control-Z` on
+Windows) at the primary prompt causes the interpreter to exit with a zero exit
+status.  If that doesn't work, you can exit the interpreter by typing the
+following command: ``quit()``.
+
+The interpreter's line-editing features include interactive editing, history
+substitution and code completion on systems that support readline.  Perhaps the
+quickest check to see whether command line editing is supported is typing
+:kbd:`Control-P` to the first Python prompt you get.  If it beeps, you have command
+line editing; see Appendix :ref:`tut-interacting` for an introduction to the
+keys.  If nothing appears to happen, or if ``^P`` is echoed, command line
+editing isn't available; you'll only be able to use backspace to remove
+characters from the current line.
+
+The interpreter operates somewhat like the Unix shell: when called with standard
+input connected to a tty device, it reads and executes commands interactively;
+when called with a file name argument or with a file as standard input, it reads
+and executes a *script* from that file.
+
+A second way of starting the interpreter is ``python -c command [arg] ...``,
+which executes the statement(s) in *command*, analogous to the shell's
+:option:`-c` option.  Since Python statements often contain spaces or other
+characters that are special to the shell, it is usually advised to quote
+*command* in its entirety with single quotes.
+
+Some Python modules are also useful as scripts.  These can be invoked using
+``python -m module [arg] ...``, which executes the source file for *module* as
+if you had spelled out its full name on the command line.
+
+When a script file is used, it is sometimes useful to be able to run the script
+and enter interactive mode afterwards.  This can be done by passing :option:`-i`
+before the script.
+
+All command line options are described in :ref:`using-on-general`.
+
+
+.. _tut-argpassing:
+
+Argument Passing
+----------------
+
+When known to the interpreter, the script name and additional arguments
+thereafter are turned into a list of strings and assigned to the ``argv``
+variable in the ``sys`` module.  You can access this list by executing ``import
+sys``.  The length of the list is at least one; when no script and no arguments
+are given, ``sys.argv[0]`` is an empty string.  When the script name is given as
+``'-'`` (meaning  standard input), ``sys.argv[0]`` is set to ``'-'``.  When
+:option:`-c` *command* is used, ``sys.argv[0]`` is set to ``'-c'``.  When
+:option:`-m` *module* is used, ``sys.argv[0]``  is set to the full name of the
+located module.  Options found after  :option:`-c` *command* or :option:`-m`
+*module* are not consumed  by the Python interpreter's option processing but
+left in ``sys.argv`` for  the command or module to handle.
+
+
+.. _tut-interactive:
+
+Interactive Mode
+----------------
+
+When commands are read from a tty, the interpreter is said to be in *interactive
+mode*.  In this mode it prompts for the next command with the *primary prompt*,
+usually three greater-than signs (``>>>``); for continuation lines it prompts
+with the *secondary prompt*, by default three dots (``...``). The interpreter
+prints a welcome message stating its version number and a copyright notice
+before printing the first prompt:
+
+.. code-block:: shell-session
+
+   $ python3.7
+   Python 3.7 (default, Sep 16 2015, 09:25:04)
+   [GCC 4.8.2] on linux
+   Type "help", "copyright", "credits" or "license" for more information.
+   >>>
+
+.. XXX update for new releases
+
+Continuation lines are needed when entering a multi-line construct. As an
+example, take a look at this :keyword:`if` statement::
+
+   >>> the_world_is_flat = True
+   >>> if the_world_is_flat:
+   ...     print("Be careful not to fall off!")
+   ...
+   Be careful not to fall off!
+
+
+For more on interactive mode, see :ref:`tut-interac`.
+
+
+.. _tut-interp:
+
+The Interpreter and Its Environment
+===================================
+
+
+.. _tut-source-encoding:
+
+Source Code Encoding
+--------------------
+
+By default, Python source files are treated as encoded in UTF-8.  In that
+encoding, characters of most languages in the world can be used simultaneously
+in string literals, identifiers and comments --- although the standard library
+only uses ASCII characters for identifiers, a convention that any portable code
+should follow.  To display all these characters properly, your editor must
+recognize that the file is UTF-8, and it must use a font that supports all the
+characters in the file.
+
+To declare an encoding other than the default one, a special comment line
+should be added as the *first* line of the file.  The syntax is as follows::
+
+   # -*- coding: encoding -*-
+
+where *encoding* is one of the valid :mod:`codecs` supported by Python.
+
+For example, to declare that Windows-1252 encoding is to be used, the first
+line of your source code file should be::
+
+   # -*- coding: cp1252 -*-
+
+One exception to the *first line* rule is when the source code starts with a
+:ref:`UNIX "shebang" line <tut-scripts>`.  In this case, the encoding
+declaration should be added as the second line of the file.  For example::
+
+   #!/usr/bin/env python3
+   # -*- coding: cp1252 -*-
+
+.. rubric:: Footnotes
+
+.. [#] On Unix, the Python 3.x interpreter is by default not installed with the
+   executable named ``python``, so that it does not conflict with a
+   simultaneously installed Python 2.x executable.