Doc/library/trace.rst
!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:
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
.. option:: --help
Display usage and exit.
.. option:: --version
Display the version of the module and exit.
.. versionadded:: 3.8
Added --module option that allows running an executable module.
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
.. option:: -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.
.. option:: -t, --trace
Display lines as they are executed.
.. option:: -l, --listfuncs
Display the functions executed by running the program.
.. option:: -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.
.. option:: -T, --trackcalls
Display the calling relationships exposed by running the program.
Modifiers ^^^^^^^^^
.. program:: trace
.. option:: -f, --file=<file>
Name of a file to accumulate counts over several tracing runs. Should be
used with the :option:--count <-c> option.
.. option:: -C, --coverdir=<dir>
Directory where the report files go. The coverage report for
package.module is written to file :file:{dir}/{package}/{module}.cover.
.. option:: -m, --missing
When generating annotated listings, mark lines which were not executed with
>>>>>>.
.. option:: -s, --summary
When using :option:--count <-c> or :option:--report <-r>, write a brief
summary to stdout for each file processed.
.. option:: -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.
.. option:: -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
.. option:: --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.
.. option:: --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:
.. 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,
*, ignore_missing_files=False)
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.
If *ignore_missing_files* is ``True``, coverage counts for files that no
longer exist are silently ignored. Otherwise, a missing file will
raise a :exc:`FileNotFoundError`.
.. versionchanged:: 3.13
Added *ignore_missing_files* parameter.
A simple example demonstrating the use of the programmatic interface::
import sys import trace
tracer = trace.Trace( ignoredirs=[sys.prefix, sys.exec_prefix], trace=0, count=1)
tracer.run('main()')
r = tracer.results() r.write_results(show_missing=True, coverdir=".")