mirror of https://github.com/python/cpython
225 lines
7.1 KiB
ReStructuredText
225 lines
7.1 KiB
ReStructuredText
:mod:`!trace` --- Trace or track Python statement execution
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===========================================================
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.. module:: trace
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:synopsis: Trace or track Python statement execution.
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**Source code:** :source:`Lib/trace.py`
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--------------
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The :mod:`trace` module allows you to trace program execution, generate
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annotated statement coverage listings, print caller/callee relationships and
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list functions executed during a program run. It can be used in another program
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or from the command line.
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.. seealso::
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`Coverage.py <https://coverage.readthedocs.io/>`_
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A popular third-party coverage tool that provides HTML
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output along with advanced features such as branch coverage.
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.. _trace-cli:
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Command-Line Usage
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------------------
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The :mod:`trace` module can be invoked from the command line. It can be as
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simple as ::
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python -m trace --count -C . somefile.py ...
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The above will execute :file:`somefile.py` and generate annotated listings of
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all Python modules imported during the execution into the current directory.
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.. program:: trace
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.. option:: --help
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Display usage and exit.
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.. option:: --version
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Display the version of the module and exit.
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.. versionadded:: 3.8
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Added ``--module`` option that allows to run an executable module.
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Main options
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^^^^^^^^^^^^
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At least one of the following options must be specified when invoking
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:mod:`trace`. The :option:`--listfuncs <-l>` option is mutually exclusive with
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the :option:`--trace <-t>` and :option:`--count <-c>` options. When
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:option:`--listfuncs <-l>` is provided, neither :option:`--count <-c>` nor
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:option:`--trace <-t>` are accepted, and vice versa.
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.. program:: trace
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.. option:: -c, --count
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Produce a set of annotated listing files upon program completion that shows
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how many times each statement was executed. See also
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:option:`--coverdir <-C>`, :option:`--file <-f>` and
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:option:`--no-report <-R>` below.
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.. option:: -t, --trace
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Display lines as they are executed.
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.. option:: -l, --listfuncs
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Display the functions executed by running the program.
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.. option:: -r, --report
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Produce an annotated list from an earlier program run that used the
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:option:`--count <-c>` and :option:`--file <-f>` option. This does not
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execute any code.
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.. option:: -T, --trackcalls
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Display the calling relationships exposed by running the program.
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Modifiers
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^^^^^^^^^
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.. program:: trace
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.. option:: -f, --file=<file>
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Name of a file to accumulate counts over several tracing runs. Should be
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used with the :option:`--count <-c>` option.
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.. option:: -C, --coverdir=<dir>
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Directory where the report files go. The coverage report for
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``package.module`` is written to file :file:`{dir}/{package}/{module}.cover`.
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.. option:: -m, --missing
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When generating annotated listings, mark lines which were not executed with
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``>>>>>>``.
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.. option:: -s, --summary
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When using :option:`--count <-c>` or :option:`--report <-r>`, write a brief
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summary to stdout for each file processed.
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.. option:: -R, --no-report
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Do not generate annotated listings. This is useful if you intend to make
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several runs with :option:`--count <-c>`, and then produce a single set of
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annotated listings at the end.
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.. option:: -g, --timing
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Prefix each line with the time since the program started. Only used while
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tracing.
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Filters
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^^^^^^^
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These options may be repeated multiple times.
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.. program:: trace
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.. option:: --ignore-module=<mod>
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Ignore each of the given module names and its submodules (if it is a
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package). The argument can be a list of names separated by a comma.
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.. option:: --ignore-dir=<dir>
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Ignore all modules and packages in the named directory and subdirectories.
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The argument can be a list of directories separated by :data:`os.pathsep`.
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.. _trace-api:
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Programmatic Interface
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----------------------
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.. class:: Trace(count=1, trace=1, countfuncs=0, countcallers=0, ignoremods=(),\
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ignoredirs=(), infile=None, outfile=None, timing=False)
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Create an object to trace execution of a single statement or expression. All
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parameters are optional. *count* enables counting of line numbers. *trace*
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enables line execution tracing. *countfuncs* enables listing of the
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functions called during the run. *countcallers* enables call relationship
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tracking. *ignoremods* is a list of modules or packages to ignore.
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*ignoredirs* is a list of directories whose modules or packages should be
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ignored. *infile* is the name of the file from which to read stored count
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information. *outfile* is the name of the file in which to write updated
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count information. *timing* enables a timestamp relative to when tracing was
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started to be displayed.
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.. method:: run(cmd)
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Execute the command and gather statistics from the execution with
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the current tracing parameters. *cmd* must be a string or code object,
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suitable for passing into :func:`exec`.
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.. method:: runctx(cmd, globals=None, locals=None)
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Execute the command and gather statistics from the execution with the
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current tracing parameters, in the defined global and local
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environments. If not defined, *globals* and *locals* default to empty
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dictionaries.
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.. method:: runfunc(func, /, *args, **kwds)
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Call *func* with the given arguments under control of the :class:`Trace`
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object with the current tracing parameters.
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.. method:: results()
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Return a :class:`CoverageResults` object that contains the cumulative
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results of all previous calls to ``run``, ``runctx`` and ``runfunc``
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for the given :class:`Trace` instance. Does not reset the accumulated
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trace results.
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.. class:: CoverageResults
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A container for coverage results, created by :meth:`Trace.results`. Should
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not be created directly by the user.
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.. method:: update(other)
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Merge in data from another :class:`CoverageResults` object.
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.. method:: write_results(show_missing=True, summary=False, coverdir=None,\
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*, ignore_missing_files=False)
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Write coverage results. Set *show_missing* to show lines that had no
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hits. Set *summary* to include in the output the coverage summary per
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module. *coverdir* specifies the directory into which the coverage
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result files will be output. If ``None``, the results for each source
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file are placed in its directory.
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If *ignore_missing_files* is ``True``, coverage counts for files that no
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longer exist are silently ignored. Otherwise, a missing file will
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raise a :exc:`FileNotFoundError`.
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.. versionchanged:: 3.13
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Added *ignore_missing_files* parameter.
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A simple example demonstrating the use of the programmatic interface::
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import sys
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import trace
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# create a Trace object, telling it what to ignore, and whether to
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# do tracing or line-counting or both.
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tracer = trace.Trace(
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ignoredirs=[sys.prefix, sys.exec_prefix],
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trace=0,
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count=1)
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# run the new command using the given tracer
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tracer.run('main()')
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# make a report, placing output in the current directory
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r = tracer.results()
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r.write_results(show_missing=True, coverdir=".")
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