ref: a8d00e5d56b261376410c3c87c46327362763bd8
dir: /sys/src/cmd/python/Doc/lib/libtrace.tex/
\section{\module{trace} ---
Trace or track Python statement execution}
\declaremodule{standard}{trace}
\modulesynopsis{Trace or track Python statement execution.}
The \module{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.
\subsection{Command Line Usage\label{trace-cli}}
The \module{trace} module can be invoked from the command line. It can be
as simple as
\begin{verbatim}
python -m trace --count somefile.py ...
\end{verbatim}
The above will generate annotated listings of all Python modules imported
during the execution of \file{somefile.py}.
The following command-line arguments are supported:
\begin{description}
\item[\longprogramopt{trace}, \programopt{-t}]
Display lines as they are executed.
\item[\longprogramopt{count}, \programopt{-c}]
Produce a set of annotated listing files upon program
completion that shows how many times each statement was executed.
\item[\longprogramopt{report}, \programopt{-r}]
Produce an annotated list from an earlier program run that
used the \longprogramopt{count} and \longprogramopt{file} arguments.
\item[\longprogramopt{no-report}, \programopt{-R}]
Do not generate annotated listings. This is useful if you intend to make
several runs with \longprogramopt{count} then produce a single set
of annotated listings at the end.
\item[\longprogramopt{listfuncs}, \programopt{-l}]
List the functions executed by running the program.
\item[\longprogramopt{trackcalls}, \programopt{-T}]
Generate calling relationships exposed by running the program.
\item[\longprogramopt{file}, \programopt{-f}]
Name a file containing (or to contain) counts.
\item[\longprogramopt{coverdir}, \programopt{-C}]
Name a directory in which to save annotated listing files.
\item[\longprogramopt{missing}, \programopt{-m}]
When generating annotated listings, mark lines which
were not executed with `\code{>>>>>>}'.
\item[\longprogramopt{summary}, \programopt{-s}]
When using \longprogramopt{count} or \longprogramopt{report}, write a
brief summary to stdout for each file processed.
\item[\longprogramopt{ignore-module}]
Ignore the named module and its submodules (if it is
a package). May be given multiple times.
\item[\longprogramopt{ignore-dir}]
Ignore all modules and packages in the named directory
and subdirectories. May be given multiple times.
\end{description}
\subsection{Programming Interface\label{trace-api}}
\begin{classdesc}{Trace}{\optional{count=1\optional{, trace=1\optional{,
countfuncs=0\optional{, countcallers=0\optional{,
ignoremods=()\optional{, ignoredirs=()\optional{,
infile=None\optional{, outfile=None}}}}}}}}}
Create an object to trace execution of a single statement or expression.
All parameters are optional. \var{count} enables counting of line numbers.
\var{trace} enables line execution tracing. \var{countfuncs} enables
listing of the functions called during the run. \var{countcallers} enables
call relationship tracking. \var{ignoremods} is a list of modules or
packages to ignore. \var{ignoredirs} is a list of directories whose modules
or packages should be ignored. \var{infile} is the file from which to read
stored count information. \var{outfile} is a file in which to write updated
count information.
\end{classdesc}
\begin{methoddesc}[Trace]{run}{cmd}
Run \var{cmd} under control of the Trace object with the current tracing
parameters.
\end{methoddesc}
\begin{methoddesc}[Trace]{runctx}{cmd\optional{, globals=None\optional{,
locals=None}}}
Run \var{cmd} under control of the Trace object with the current tracing
parameters in the defined global and local environments. If not defined,
\var{globals} and \var{locals} default to empty dictionaries.
\end{methoddesc}
\begin{methoddesc}[Trace]{runfunc}{func, *args, **kwds}
Call \var{func} with the given arguments under control of the
\class{Trace} object with the current tracing parameters.
\end{methoddesc}
This is a simple example showing the use of this module:
\begin{verbatim}
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 /tmp
r = tracer.results()
r.write_results(show_missing=True, coverdir="/tmp")
\end{verbatim}