1 :mod:`trace` --- Trace or track Python statement execution 2 ========================================================== 3 4 .. module:: trace 5 :synopsis: Trace or track Python statement execution. 6 7 **Source code:** :source:`Lib/trace.py` 8 9 -------------- 10 11 The :mod:`trace` module allows you to trace program execution, generate 12 annotated statement coverage listings, print caller/callee relationships and 13 list functions executed during a program run. It can be used in another program 14 or from the command line. 15 16 .. seealso:: 17 18 `Coverage.py <https://coverage.readthedocs.io/>`_ 19 A popular third-party coverage tool that provides HTML 20 output along with advanced features such as branch coverage. 21 22 .. _trace-cli: 23 24 Command-Line Usage 25 ------------------ 26 27 The :mod:`trace` module can be invoked from the command line. It can be as 28 simple as :: 29 30 python -m trace --count -C . somefile.py ... 31 32 The above will execute :file:`somefile.py` and generate annotated listings of 33 all Python modules imported during the execution into the current directory. 34 35 .. program:: trace 36 37 .. cmdoption:: --help 38 39 Display usage and exit. 40 41 .. cmdoption:: --version 42 43 Display the version of the module and exit. 44 45 Main options 46 ^^^^^^^^^^^^ 47 48 At least one of the following options must be specified when invoking 49 :mod:`trace`. The :option:`--listfuncs <-l>` option is mutually exclusive with 50 the :option:`--trace <-t>` and :option:`--count <-c>` options. When 51 :option:`--listfuncs <-l>` is provided, neither :option:`--count <-c>` nor 52 :option:`--trace <-t>` are accepted, and vice versa. 53 54 .. program:: trace 55 56 .. cmdoption:: -c, --count 57 58 Produce a set of annotated listing files upon program completion that shows 59 how many times each statement was executed. See also 60 :option:`--coverdir <-C>`, :option:`--file <-f>` and 61 :option:`--no-report <-R>` below. 62 63 .. cmdoption:: -t, --trace 64 65 Display lines as they are executed. 66 67 .. cmdoption:: -l, --listfuncs 68 69 Display the functions executed by running the program. 70 71 .. cmdoption:: -r, --report 72 73 Produce an annotated list from an earlier program run that used the 74 :option:`--count <-c>` and :option:`--file <-f>` option. This does not 75 execute any code. 76 77 .. cmdoption:: -T, --trackcalls 78 79 Display the calling relationships exposed by running the program. 80 81 Modifiers 82 ^^^^^^^^^ 83 84 .. program:: trace 85 86 .. cmdoption:: -f, --file=<file> 87 88 Name of a file to accumulate counts over several tracing runs. Should be 89 used with the :option:`--count <-c>` option. 90 91 .. cmdoption:: -C, --coverdir=<dir> 92 93 Directory where the report files go. The coverage report for 94 ``package.module`` is written to file :file:`{dir}/{package}/{module}.cover`. 95 96 .. cmdoption:: -m, --missing 97 98 When generating annotated listings, mark lines which were not executed with 99 ``>>>>>>``. 100 101 .. cmdoption:: -s, --summary 102 103 When using :option:`--count <-c>` or :option:`--report <-r>`, write a brief 104 summary to stdout for each file processed. 105 106 .. cmdoption:: -R, --no-report 107 108 Do not generate annotated listings. This is useful if you intend to make 109 several runs with :option:`--count <-c>`, and then produce a single set of 110 annotated listings at the end. 111 112 .. cmdoption:: -g, --timing 113 114 Prefix each line with the time since the program started. Only used while 115 tracing. 116 117 Filters 118 ^^^^^^^ 119 120 These options may be repeated multiple times. 121 122 .. program:: trace 123 124 .. cmdoption:: --ignore-module=<mod> 125 126 Ignore each of the given module names and its submodules (if it is a 127 package). The argument can be a list of names separated by a comma. 128 129 .. cmdoption:: --ignore-dir=<dir> 130 131 Ignore all modules and packages in the named directory and subdirectories. 132 The argument can be a list of directories separated by :data:`os.pathsep`. 133 134 .. _trace-api: 135 136 Programmatic Interface 137 ---------------------- 138 139 .. class:: Trace(count=1, trace=1, countfuncs=0, countcallers=0, ignoremods=(),\ 140 ignoredirs=(), infile=None, outfile=None, timing=False) 141 142 Create an object to trace execution of a single statement or expression. All 143 parameters are optional. *count* enables counting of line numbers. *trace* 144 enables line execution tracing. *countfuncs* enables listing of the 145 functions called during the run. *countcallers* enables call relationship 146 tracking. *ignoremods* is a list of modules or packages to ignore. 147 *ignoredirs* is a list of directories whose modules or packages should be 148 ignored. *infile* is the name of the file from which to read stored count 149 information. *outfile* is the name of the file in which to write updated 150 count information. *timing* enables a timestamp relative to when tracing was 151 started to be displayed. 152 153 .. method:: run(cmd) 154 155 Execute the command and gather statistics from the execution with 156 the current tracing parameters. *cmd* must be a string or code object, 157 suitable for passing into :func:`exec`. 158 159 .. method:: runctx(cmd, globals=None, locals=None) 160 161 Execute the command and gather statistics from the execution with the 162 current tracing parameters, in the defined global and local 163 environments. If not defined, *globals* and *locals* default to empty 164 dictionaries. 165 166 .. method:: runfunc(func, *args, **kwds) 167 168 Call *func* with the given arguments under control of the :class:`Trace` 169 object with the current tracing parameters. 170 171 .. method:: results() 172 173 Return a :class:`CoverageResults` object that contains the cumulative 174 results of all previous calls to ``run``, ``runctx`` and ``runfunc`` 175 for the given :class:`Trace` instance. Does not reset the accumulated 176 trace results. 177 178 .. class:: CoverageResults 179 180 A container for coverage results, created by :meth:`Trace.results`. Should 181 not be created directly by the user. 182 183 .. method:: update(other) 184 185 Merge in data from another :class:`CoverageResults` object. 186 187 .. method:: write_results(show_missing=True, summary=False, coverdir=None) 188 189 Write coverage results. Set *show_missing* to show lines that had no 190 hits. Set *summary* to include in the output the coverage summary per 191 module. *coverdir* specifies the directory into which the coverage 192 result files will be output. If ``None``, the results for each source 193 file are placed in its directory. 194 195 A simple example demonstrating the use of the programmatic interface:: 196 197 import sys 198 import trace 199 200 # create a Trace object, telling it what to ignore, and whether to 201 # do tracing or line-counting or both. 202 tracer = trace.Trace( 203 ignoredirs=[sys.prefix, sys.exec_prefix], 204 trace=0, 205 count=1) 206 207 # run the new command using the given tracer 208 tracer.run('main()') 209 210 # make a report, placing output in the current directory 211 r = tracer.results() 212 r.write_results(show_missing=True, coverdir=".") 213 214
