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python-3.7.4-docs-html/_sources/library/trace.rst.txt

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+:mod:`trace` --- Trace or track Python statement execution
+==========================================================
+
+.. module:: trace
+   :synopsis: Trace or track Python statement execution.
+
+**Source code:** :source:`Lib/trace.py`
+
+--------------
+
+The :mod:`trace` module allows you to trace program execution, generate
+annotated statement coverage listings, print caller/callee relationships and
+list functions executed during a program run.  It can be used in another program
+or from the command line.
+
+.. seealso::
+
+   `Coverage.py <https://coverage.readthedocs.io/>`_
+      A popular third-party coverage tool that provides HTML
+      output along with advanced features such as branch coverage.
+
+.. _trace-cli:
+
+Command-Line Usage
+------------------
+
+The :mod:`trace` module can be invoked from the command line.  It can be as
+simple as ::
+
+   python -m trace --count -C . somefile.py ...
+
+The above will execute :file:`somefile.py` and generate annotated listings of
+all Python modules imported during the execution into the current directory.
+
+.. program:: trace
+
+.. cmdoption:: --help
+
+   Display usage and exit.
+
+.. cmdoption:: --version
+
+   Display the version of the module and exit.
+
+Main options
+^^^^^^^^^^^^
+
+At least one of the following options must be specified when invoking
+:mod:`trace`.  The :option:`--listfuncs <-l>` option is mutually exclusive with
+the :option:`--trace <-t>` and :option:`--count <-c>` options. When
+:option:`--listfuncs <-l>` is provided, neither :option:`--count <-c>` nor
+:option:`--trace <-t>` are accepted, and vice versa.
+
+.. program:: trace
+
+.. cmdoption:: -c, --count
+
+   Produce a set of annotated listing files upon program completion that shows
+   how many times each statement was executed.  See also
+   :option:`--coverdir <-C>`, :option:`--file <-f>` and
+   :option:`--no-report <-R>` below.
+
+.. cmdoption:: -t, --trace
+
+   Display lines as they are executed.
+
+.. cmdoption:: -l, --listfuncs
+
+   Display the functions executed by running the program.
+
+.. cmdoption:: -r, --report
+
+   Produce an annotated list from an earlier program run that used the
+   :option:`--count <-c>` and :option:`--file <-f>` option.  This does not
+   execute any code.
+
+.. cmdoption:: -T, --trackcalls
+
+   Display the calling relationships exposed by running the program.
+
+Modifiers
+^^^^^^^^^
+
+.. program:: trace
+
+.. cmdoption:: -f, --file=<file>
+
+   Name of a file to accumulate counts over several tracing runs.  Should be
+   used with the :option:`--count <-c>` option.
+
+.. cmdoption:: -C, --coverdir=<dir>
+
+   Directory where the report files go.  The coverage report for
+   ``package.module`` is written to file :file:`{dir}/{package}/{module}.cover`.
+
+.. cmdoption:: -m, --missing
+
+   When generating annotated listings, mark lines which were not executed with
+   ``>>>>>>``.
+
+.. cmdoption:: -s, --summary
+
+   When using :option:`--count <-c>` or :option:`--report <-r>`, write a brief
+   summary to stdout for each file processed.
+
+.. cmdoption:: -R, --no-report
+
+   Do not generate annotated listings.  This is useful if you intend to make
+   several runs with :option:`--count <-c>`, and then produce a single set of
+   annotated listings at the end.
+
+.. cmdoption:: -g, --timing
+
+   Prefix each line with the time since the program started.  Only used while
+   tracing.
+
+Filters
+^^^^^^^
+
+These options may be repeated multiple times.
+
+.. program:: trace
+
+.. cmdoption:: --ignore-module=<mod>
+
+   Ignore each of the given module names and its submodules (if it is a
+   package).  The argument can be a list of names separated by a comma.
+
+.. cmdoption:: --ignore-dir=<dir>
+
+   Ignore all modules and packages in the named directory and subdirectories.
+   The argument can be a list of directories separated by :data:`os.pathsep`.
+
+.. _trace-api:
+
+Programmatic Interface
+----------------------
+
+.. class:: Trace(count=1, trace=1, countfuncs=0, countcallers=0, ignoremods=(),\
+                 ignoredirs=(), infile=None, outfile=None, timing=False)
+
+   Create an object to trace execution of a single statement or expression.  All
+   parameters are optional.  *count* enables counting of line numbers.  *trace*
+   enables line execution tracing.  *countfuncs* enables listing of the
+   functions called during the run.  *countcallers* enables call relationship
+   tracking.  *ignoremods* is a list of modules or packages to ignore.
+   *ignoredirs* is a list of directories whose modules or packages should be
+   ignored.  *infile* is the name of the file from which to read stored count
+   information.  *outfile* is the name of the file in which to write updated
+   count information.  *timing* enables a timestamp relative to when tracing was
+   started to be displayed.
+
+    .. method:: run(cmd)
+
+       Execute the command and gather statistics from the execution with
+       the current tracing parameters.  *cmd* must be a string or code object,
+       suitable for passing into :func:`exec`.
+
+    .. method:: runctx(cmd, globals=None, locals=None)
+
+       Execute the command and gather statistics from the execution with the
+       current tracing parameters, in the defined global and local
+       environments.  If not defined, *globals* and *locals* default to empty
+       dictionaries.
+
+    .. method:: runfunc(func, *args, **kwds)
+
+       Call *func* with the given arguments under control of the :class:`Trace`
+       object with the current tracing parameters.
+
+    .. method:: results()
+
+       Return a :class:`CoverageResults` object that contains the cumulative
+       results of all previous calls to ``run``, ``runctx`` and ``runfunc``
+       for the given :class:`Trace` instance.  Does not reset the accumulated
+       trace results.
+
+.. class:: CoverageResults
+
+   A container for coverage results, created by :meth:`Trace.results`.  Should
+   not be created directly by the user.
+
+    .. method:: update(other)
+
+       Merge in data from another :class:`CoverageResults` object.
+
+    .. method:: write_results(show_missing=True, summary=False, coverdir=None)
+
+       Write coverage results.  Set *show_missing* to show lines that had no
+       hits.  Set *summary* to include in the output the coverage summary per
+       module.  *coverdir* specifies the directory into which the coverage
+       result files will be output.  If ``None``, the results for each source
+       file are placed in its directory.
+
+A simple example demonstrating the use of the programmatic interface::
+
+   import sys
+   import trace
+
+   # create a Trace object, telling it what to ignore, and whether to
+   # do tracing or line-counting or both.
+   tracer = trace.Trace(
+       ignoredirs=[sys.prefix, sys.exec_prefix],
+       trace=0,
+       count=1)
+
+   # run the new command using the given tracer
+   tracer.run('main()')
+
+   # make a report, placing output in the current directory
+   r = tracer.results()
+   r.write_results(show_missing=True, coverdir=".")
+