Major change history for

These are the major changes for For a more complete change history, see the CHANGES.rst file in the source tree.

Version 4.0.2 — 4 November 2015

  • More work on supporting unusually encoded source. Fixed issue 431.
  • Files or directories with non-ASCII characters are now handled properly, fixing issue 432.
  • Setting a trace function with sys.settrace was broken by a change in 4.0.1, as reported in issue 436. This is now fixed.
  • Officially support PyPy 4.0, which required no changes, just updates to the docs.

Version 4.0.1 — 13 October 2015

  • When combining data files, unreadable files will now generate a warning instead of failing the command. This is more in line with the older v3.7.1 behavior, which silently ignored unreadable files. Prompted by issue 418.
  • The –skip-covered option would skip reporting on 100% covered files, but also skipped them when calculating total coverage. This was wrong, it should only remove lines from the report, not change the final answer. This is now fixed, closing issue 423.
  • In 4.0, the data file recorded a summary of the system on which it was run. Combined data files would keep all of those summaries. This could lead to enormous data files consisting of mostly repetitive useless information. That summary is now gone, fixing issue 415. If you want summary information, get in touch, and we’ll figure out a better way to do it.
  • Test suites that mocked os.path.exists would experience strange failures, due to using their mock inadvertently. This is now fixed, closing issue 416.
  • Importing a __init__ module explicitly would lead to an error: AttributeError: 'module' object has no attribute '__path__', as reported in issue 410. This is now fixed.
  • Code that uses sys.settrace(sys.gettrace()) used to incur a more than 2x speed penalty. Now there’s no penalty at all. Fixes issue 397.
  • Pyexpat C code will no longer be recorded as a source file, fixing issue 419.
  • The source kit now contains all of the files needed to have a complete source tree, re-fixing issue 137 and closing issue 281.

Version 4.0 — 20 September 2015

Backward incompatibilities:

  • Python versions supported are now:
    • CPython 2.6, 2.7, 3.3, 3.4 and 3.5
    • PyPy2 2.4, 2.6
    • PyPy3 2.4
  • The original command line switches (-x to run a program, etc) are no longer supported.
  • The COVERAGE_OPTIONS environment variable is no longer supported. It was a hack for --timid before configuration files were available.
  • The original module-level function interface to is no longer supported. You must now create a coverage.Coverage object, and use methods on it.
  • The Coverage.use_cache method is no longer supported.
  • The private method Coverage._harvest_data is now called Coverage.get_data(), and returns the CoverageData containing the collected data.
  • is now licensed under the Apache 2.0 license. See NOTICE.txt for details.
  • kits no longer include tests and docs. If you were using them, get in touch and let me know how.

Major new features:

  • Plugins: third parties can write plugins to add file support for non-Python files, such as web application templating engines, or languages that compile down to Python. See Plugins for how to use plugins, and Plugin classes for details of how to write them. A plugin for measuring Django template coverage is available: django_coverage_plugin
  • Gevent, eventlet, and greenlet are now supported. The [run] concurrency setting, or the --concurrency command line switch, specifies the concurrency library in use. Huge thanks to Peter Portante for initial implementation, and to Joe Jevnik for the final insight that completed the work.
  • The data storage has been re-written, using JSON instead of pickle. The CoverageData class is a new supported API to the contents of the data file. Data files from older versions of can be converted to the new format with python -m coverage.pickle2json.
  • Wildly experimental: support for measuring processes started by the multiprocessing module. To use, set --concurrency=multiprocessing, either on the command line or in the .coveragerc file. Thanks, Eduardo Schettino. Currently, this does not work on Windows.

New features:

  • Options are now also read from a setup.cfg file, if any. Sections are prefixed with “coverage:”, so the [run] options will be read from the [coverage:run] section of setup.cfg.
  • The HTML report now has filtering. Type text into the Filter box on the index page, and only modules with that text in the name will be shown. Thanks, Danny Allen.
  • A new option: coverage report --skip-covered (or [report] skip_covered) will reduce the number of files reported by skipping files with 100% coverage. Thanks, Krystian Kichewko. This means that empty files will be skipped, since they are 100% covered.
  • You can now specify the --fail-under option in the .coveragerc file as the [report] fail_under option.
  • The report -m command now shows missing branches when reporting on branch coverage. Thanks, Steve Leonard.
  • The coverage combine command now accepts any number of directories or files as arguments, and will combine all the data from them. This means you don’t have to copy the files to one directory before combining. Thanks, Christine Lytwynec.
  • A new configuration option for the XML report: [xml] package_depth controls which directories are identified as packages in the report. Directories deeper than this depth are not reported as packages. The default is that all directories are reported as packages. Thanks, Lex Berezhny.
  • A new configuration option, [run] note, lets you set a note that will be stored in the runs section of the data file. You can use this to annotate the data file with any information you like.
  • The COVERAGE_DEBUG environment variable can be used to set the [run] debug configuration option to control what internal operations are logged.
  • A new version identifier is available, coverage.version_info, a plain tuple of values similar to sys.version_info.


  • now always adds the current directory to sys.path, so that plugins can import files in the current directory.
  • now accepts a directory name for coverage run and will run a found there, just like Python will. Thanks, Dmitry Trofimov.
  • The --debug switch can now be used on any command.
  • Reports now use file names with extensions. Previously, a report would describe a/b/ as “a/b/c”. Now it is shown as “a/b/”. This allows for better support of non-Python files.
  • Missing branches in the HTML report now have a bit more information in the right-hand annotations. Hopefully this will make their meaning clearer.
  • The XML report now contains a <source> element. Thanks Stan Hu.
  • The XML report now includes a missing-branches attribute. Thanks, Steve Peak. This is not a part of the Cobertura DTD, so the XML report no longer references the DTD.
  • The XML report now reports each directory as a package again. This was a bad regression, I apologize.
  • In parallel mode, coverage erase will now delete all of the data files.
  • A new warning is possible, if a desired file isn’t measured because it was imported before was started.
  • The coverage.process_startup() function now will start coverage measurement only once, no matter how many times it is called. This fixes problems due to unusual virtualenv configurations.
  • Unrecognized configuration options will now print an error message and stop This should help prevent configuration mistakes from passing silently.

API changes:

  • The class defined in the coverage module is now called Coverage instead of coverage, though the old name still works, for backward compatibility.
  • You can now programmatically adjust the configuration of by calling Coverage.set_option() after construction. Coverage.get_option() reads the configuration values.
  • If the config_file argument to the Coverage constructor is specified as ”.coveragerc”, it is treated as if it were True. This means setup.cfg is also examined, and a missing file is not considered an error.

Bug fixes:

  • The textual report and the HTML report used to report partial branches differently for no good reason. Now the text report’s “missing branches” column is a “partial branches” column so that both reports show the same numbers. This closes issue 342.
  • The fail-under value is now rounded the same as reported results, preventing paradoxical results, fixing issue 284.
  • Branch coverage couldn’t properly handle certain extremely long files. This is now fixed, closing issue 359.
  • Branch coverage didn’t understand yield statements properly. Mickie Betz persisted in pursuing this despite Ned’s pessimism. Fixes issue 308 and issue 324.
  • Files with incorrect encoding declaration comments are no longer ignored by the reporting commands.
  • Empty files are now reported as 100% covered in the XML report, not 0% covered.
  • The XML report will now create the output directory if need be. Thanks, Chris Rose.
  • HTML reports no longer raise UnicodeDecodeError if a Python file has undecodable characters.
  • The annotate command will now annotate all files, not just ones relative to the current directory.

Version 3.7.1 — 13 December 2013

  • Improved the speed of HTML report generation by about 20%.
  • Fixed the mechanism for finding OS-installed static files for the HTML report so that it will actually find OS-installed static files.

Version 3.7 — 6 October 2013

  • Added the --debug switch to coverage run. It accepts a list of options indicating the type of internal activity to log to stderr. For details, see the run –debug options.
  • Improved the branch coverage facility, fixing issue 92 and issue 175.
  • Running code with coverage run -m now behaves more like Python does, setting sys.path properly, which fixes issue 207 and issue 242.
  • can now run .pyc files directly, closing issue 264.
  • properly supports .pyw files, fixing issue 261.
  • Omitting files within a tree specified with the source option would cause them to be incorrectly marked as unexecuted, as described in issue 218. This is now fixed.
  • When specifying paths to alias together during data combining, you can now specify relative paths, fixing issue 267.
  • Most file paths can now be specified with username expansion (~/src, or ~build/src, for example), and with environment variable expansion (build/$BUILDNUM/src).
  • Trying to create an XML report with no files to report on, would cause a ZeroDivideError, but no longer does, fixing issue 250.
  • When running a threaded program under the Python tracer, no longer issues a spurious warning about the trace function changing: “Trace function changed, measurement is likely wrong: None.” This fixes issue 164.
  • Static files necessary for HTML reports are found in system-installed places, to ease OS-level packaging of Closes issue 259.
  • Source files with encoding declarations, but a blank first line, were not decoded properly. Now they are. Thanks, Roger Hu.
  • The source kit now includes the file in the root coverage directory, fixing issue 255.

Version 3.6 — 5 January 2013


  • The report, html, and xml commands now accept a --fail-under switch that indicates in the exit status whether the coverage percentage was less than a particular value. Closes issue 139.
  • The reporting functions, coverage.html_report(), and coverage.xml_report() now all return a float, the total percentage covered measurement.
  • The HTML report’s title can now be set in the configuration file, with the --title switch on the command line, or via the API.
  • Configuration files now support substitution of environment variables, using syntax like ${WORD}. Closes issue 97.


  • The C extension is optionally compiled using a different more widely-used technique, taking another stab at fixing issue 80 once and for all.
  • When installing, now in addition to creating a “coverage” command, two new aliases are also installed. A “coverage2” or “coverage3” command will be created, depending on whether you are installing in Python 2.x or 3.x. A “coverage-X.Y” command will also be created corresponding to your specific version of Python. Closes issue 111.
  • The installer no longer tries to bootstrap setuptools or Distribute. You must have one of them installed first, as issue 202 recommended.
  • The kit now includes docs (closing issue 137) and tests.


  • Added a page to the docs about contributing to, closing issue 171.
  • Added a page to the docs about troublesome situations, closing issue 226.
  • Docstrings for the legacy singleton methods are more helpful. Thanks Marius Gedminas. Closes issue 205.
  • The pydoc tool can now show documentation for the class coverage.coverage. Closes issue 206.
  • Added some info to the TODO file, closing issue 227.


  • Wildcards in include= and omit= arguments were not handled properly in reporting functions, though they were when running. Now they are handled uniformly, closing issue 143 and issue 163. NOTE: it is possible that your configurations may now be incorrect. If you use include or omit during reporting, whether on the command line, through the API, or in a configuration file, please check carefully that you were not relying on the old broken behavior.
  • Embarrassingly, the [xml] output= setting in the .coveragerc file simply didn’t work. Now it does.
  • Combining data files would create entries for phantom files if used with source and path aliases. It no longer does.
  • debug sys now shows the configuration file path that was read.
  • If an oddly-behaved package claims that code came from an empty-string file name, no longer associates it with the directory name, fixing issue 221.
  • The XML report now consistently uses file names for the filename attribute, rather than sometimes using module names. Fixes issue 67. Thanks, Marcus Cobden.
  • Coverage percentage metrics are now computed slightly differently under branch coverage. This means that completely unexecuted files will now correctly have 0% coverage, fixing issue 156. This also means that your total coverage numbers will generally now be lower if you are measuring branch coverage.
  • On Windows, files are now reported in their correct case, fixing issue 89 and issue 203.
  • If a file is missing during reporting, the path shown in the error message is now correct, rather than an incorrect path in the current directory. Fixes issue 60.
  • Running an HTML report in Python 3 in the same directory as an old Python 2 HTML report would fail with a UnicodeDecodeError. This issue (issue 193) is now fixed.
  • Fixed yet another error trying to parse non-Python files as Python, this time an IndentationError, closing issue 82 for the fourth time...
  • If coverage xml fails because there is no data to report, it used to create a zero-length XML file. Now it doesn’t, fixing issue 210.
  • Jython files now work with the --source option, fixing issue 100.
  • Running under a debugger is unlikely to work, but it shouldn’t fail with “TypeError: ‘NoneType’ object is not iterable”. Fixes issue 201.
  • On some Linux distributions, when installed with the OS package manager, would report its own code as part of the results. Now it won’t, fixing issue 214, though this will take some time to be repackaged by the operating systems.
  • When ended unsuccessfully, it may have reported odd errors like 'NoneType' object has no attribute 'isabs'. It no longer does, so kiss issue 153 goodbye.

Version 3.5.3 — 29 September 2012

  • Line numbers in the HTML report line up better with the source lines, fixing issue 197, thanks Marius Gedminas.
  • When specifying a directory as the source= option, the directory itself no longer needs to have a file, though its sub-directories do, to be considered as source files.
  • Files encoded as UTF-8 with a BOM are now properly handled, fixing issue 179. Thanks, Pablo Carballo.
  • Fixed more cases of non-Python files being reported as Python source, and then not being able to parse them as Python. Closes issue 82 (again). Thanks, Julian Berman.
  • Fixed memory leaks under Python 3, thanks, Brett Cannon. Closes issue 147.
  • Optimized .pyo files may not have been handled correctly, issue 195. Thanks, Marius Gedminas.
  • Certain unusually named file paths could have been mangled during reporting, issue 194. Thanks, Marius Gedminas.
  • Try to do a better job of the impossible task of detecting when we can’t build the C extension, fixing issue 183.

Version 3.5.2 — 4 May 2012

  • The HTML report has slightly tweaked controls: the buttons at the top of the page are color-coded to the source lines they affect.
  • Custom CSS can be applied to the HTML report by specifying a CSS file as the extra_css configuration value in the [html] section.
  • Source files with custom encodings declared in a comment at the top are now properly handled during reporting on Python 2. Python 3 always handled them properly. This fixes issue 157.
  • Backup files left behind by editors are no longer collected by the source= option, fixing issue 168.
  • If a file doesn’t parse properly as Python, we don’t report it as an error if the file name seems like maybe it wasn’t meant to be Python. This is a pragmatic fix for issue 82.
  • The -m switch on coverage report, which includes missing line numbers in the summary report, can now be specified as show_missing in the config file. Closes issue 173.
  • When running a module with coverage run -m <modulename>, certain details of the execution environment weren’t the same as for python -m <modulename>. This had the unfortunate side-effect of making coverage run -m unittest discover not work if you had tests in a directory named “test”. This fixes issue 155.
  • Now the exit status of your product code is properly used as the process status when running python -m coverage run .... Thanks, JT Olds.
  • When installing into pypy, we no longer attempt (and fail) to compile the C tracer function, closing issue 166.

Version 3.5.1 — 23 September 2011

  • When combining data files from parallel runs, you can now instruct about which directories are equivalent on different machines. A [paths] section in the configuration file lists paths that are to be considered equivalent. Finishes issue 17.
  • for-else constructs are understood better, and don’t cause erroneous partial branch warnings. Fixes issue 122.
  • Branch coverage for with statements is improved, fixing issue 128.
  • The number of partial branches reported on the HTML summary page was different than the number reported on the individual file pages. This is now fixed.
  • An explicit include directive to measure files in the Python installation wouldn’t work because of the standard library exclusion. Now the include directive takes precedence, and the files will be measured. Fixes issue 138.
  • The HTML report now handles Unicode characters in Python source files properly. This fixes issue 124 and issue 144. Thanks, Devin Jeanpierre.
  • In order to help the core developers measure the test coverage of the standard library, Brandon Rhodes devised an aggressive hack to trick Python into running some code before anything else in the process. See the coverage/fullcoverage directory if you are interested.

Version 3.5 — 29 June 2011

HTML reporting:

  • The HTML report now has hotkeys. Try n, s, m, x, b, p, and c on the overview page to change the column sorting. On a file page, r, m, x, and p toggle the run, missing, excluded, and partial line markings. You can navigate the highlighted sections of code by using the j and k keys for next and previous. The 1 (one) key jumps to the first highlighted section in the file, and 0 (zero) scrolls to the top of the file.
  • HTML reporting is now incremental: a record is kept of the data that produced the HTML reports, and only files whose data has changed will be generated. This should make most HTML reporting faster.

Running Python files

  • Modules can now be run directly using coverage run -m modulename, to mirror Python’s -m flag. Closes issue 95, thanks, Brandon Rhodes.
  • coverage run didn’t emulate Python accurately in one detail: the current directory inserted into sys.path was relative rather than absolute. This is now fixed.
  • Pathological code execution could disable the trace function behind our backs, leading to incorrect code measurement. Now if this happens, will issue a warning, at least alerting you to the problem. Closes issue 93. Thanks to Marius Gedminas for the idea.
  • The C-based trace function now behaves properly when saved and restored with sys.gettrace() and sys.settrace(). This fixes issue 125 and issue 123. Thanks, Devin Jeanpierre.
  • can now be run directly from a working tree by specifying the directory name to python: python coverage_py_working_dir run .... Thanks, Brett Cannon.
  • A little bit of Jython support: coverage run can now measure Jython execution by adapting when $py.class files are traced. Thanks, Adi Roiban.


  • Partial branch warnings can now be pragma’d away. The configuration option partial_branches is a list of regular expressions. Lines matching any of those expressions will never be marked as a partial branch. In addition, there’s a built-in list of regular expressions marking statements which should never be marked as partial. This list includes while True:, while 1:, if 1:, and if 0:.
  • The --omit and --include switches now interpret their values more usefully. If the value starts with a wildcard character, it is used as-is. If it does not, it is interpreted relative to the current directory. Closes issue 121.
  • Syntax errors in supposed Python files can now be ignored during reporting with the -i switch just like other source errors. Closes issue 115.

Version 3.4 — 19 September 2010

Controlling source:

  • BACKWARD INCOMPATIBILITY: the --omit and --include switches now take file patterns rather than file prefixes, closing issue 34 and issue 36.
  • BACKWARD INCOMPATIBILITY: the omit_prefixes argument is gone throughout, replaced with omit, a list of file name patterns suitable for fnmatch. A parallel argument include controls what files are included.
  • The run command now has a --source switch, a list of directories or module names. If provided, will only measure execution in those source files. The run command also now supports --include and --omit to control what modules it measures. This can speed execution and reduce the amount of data during reporting. Thanks Zooko.
  • The reporting commands (report, annotate, html, and xml) now have an --include switch to restrict reporting to modules matching those file patterns, similar to the existing --omit switch. Thanks, Zooko.


  • Completely unexecuted files can now be included in coverage results, reported as 0% covered. This only happens if the –source option is specified, since needs guidance about where to look for source files.
  • Python files with no statements, for example, empty files, are now reported as having zero statements instead of one. Fixes issue 1.
  • Reports now have a column of missed line counts rather than executed line counts, since developers should focus on reducing the missed lines to zero, rather than increasing the executed lines to varying targets. Once suggested, this seemed blindingly obvious.
  • Coverage percentages are now displayed uniformly across reporting methods. Previously, different reports could round percentages differently. Also, percentages are only reported as 0% or 100% if they are truly 0 or 100, and are rounded otherwise. Fixes issue 41 and issue 70.
  • The XML report output now properly includes a percentage for branch coverage, fixing issue 65 and issue 81, and the report is sorted by package name, fixing issue 88.
  • The XML report is now sorted by package name, fixing issue 88.
  • The precision of reported coverage percentages can be set with the [report] precision config file setting. Completes issue 16.
  • Line numbers in HTML source pages are clickable, linking directly to that line, which is highlighted on arrival. Added a link back to the index page at the bottom of each HTML page.

Execution and measurement:

  • Various warnings are printed to stderr for problems encountered during data measurement: if a --source module has no Python source to measure, or is never encountered at all, or if no data is collected.
  • Doctest text files are no longer recorded in the coverage data, since they can’t be reported anyway. Fixes issue 52 and issue 61.
  • Threads derived from threading.Thread with an overridden run method would report no coverage for the run method. This is now fixed, closing issue 85.
  • Programs that exited with sys.exit() with no argument weren’t handled properly, producing a stack trace. This is now fixed.
  • Programs that call os.fork will properly collect data from both the child and parent processes. Use coverage run -p to get two data files that can be combined with coverage combine. Fixes issue 56.
  • When measuring code running in a virtualenv, most of the system library was being measured when it shouldn’t have been. This is now fixed.
  • can now be run as a module: python -m coverage. Thanks, Brett Cannon.

Version 3.3.1 — 6 March 2010

  • Using parallel=True in a .coveragerc file prevented reporting, but now does not, fixing issue 49.
  • When running your code with coverage run, if you call sys.exit(), will exit with that status code, fixing issue 50.

Version 3.3 — 24 February 2010

  • Settings are now read from a .coveragerc file. A specific file can be specified on the command line with --rcfile=FILE. The name of the file can be programmatically set with the config_file argument to the coverage() constructor, or reading a config file can be disabled with config_file=False.
  • Added coverage.process_start to enable coverage measurement when Python starts.
  • Parallel data file names now have a random number appended to them in addition to the machine name and process id. Also, parallel data files combined with coverage combine are deleted after they’re combined, to clean up unneeded files. Fixes issue 40.
  • Exceptions thrown from product code run with coverage run are now displayed without internal frames, so the output is the same as when the code is run without
  • Fixed issue 39 and issue 47.

Version 3.2 — 5 December 2009

  • Branch coverage: can tell you which branches didn’t have both (or all) choices executed, even where the choice doesn’t affect which lines were executed. See Branch coverage measurement for more details.
  • The table of contents in the HTML report is now sortable: click the headers on any column. The sorting is persisted so that subsequent reports are sorted as you wish. Thanks, Chris Adams.
  • XML reporting has file paths that let Cobertura find the source code, fixing issue 21.
  • The --omit option now works much better than before, fixing issue 14 and issue 33. Thanks, Danek Duvall.
  • Added a --version option on the command line.
  • Program execution under is a few percent faster.
  • Some exceptions reported by the command line interface have been cleaned up so that tracebacks inside aren’t shown. Fixes issue 23.
  • Fixed some problems syntax coloring sources with line continuations and source with tabs: issue 30 and issue 31.

Version 3.1 — 4 October 2009

  • Python 3.1 is now supported.
  • has a new command line syntax with sub-commands. This expands the possibilities for adding features and options in the future. The old syntax is still supported. Try coverage help to see the new commands. Thanks to Ben Finney for early help.
  • Added an experimental coverage xml command for producing coverage reports in a Cobertura-compatible XML format. Thanks, Bill Hart.
  • Added the --timid option to enable a simpler slower trace function that works for DecoratorTools projects, including TurboGears. Fixed issue 12 and issue 13.
  • HTML reports now display syntax-colored Python source.
  • Added a coverage debug command for getting diagnostic information about the installation.
  • Source code can now be read from eggs. Thanks, Ross Lawley. Fixes issue 25.

Version 3.0.1 — 7 July 2009

  • Removed the recursion limit in the tracer function. Previously, code that ran more than 500 frames deep would crash.
  • Fixed a bizarre problem involving pyexpat, whereby lines following XML parser invocations could be overlooked.
  • On Python 2.3, could mis-measure code with exceptions being raised. This is now fixed.
  • The code itself will now not be measured by, and no modules will be mentioned in the nose --with-cover plugin.
  • When running source files, now opens them in universal newline mode just like Python does. This lets it run Windows files on Mac, for example.

Version 3.0 — 13 June 2009

  • is now a package rather than a module. Functionality has been split into classes.
  • HTML reports and annotation of source files: use the new -b (browser) switch. Thanks to George Song for code, inspiration and guidance.
  • The trace function is implemented in C for speed. runs are now much faster. Thanks to David Christian for productive micro-sprints and other encouragement.
  • The minimum supported Python version is 2.3.
  • When using the object API (that is, constructing a coverage() object), data is no longer saved automatically on process exit. You can re-enable it with the auto_data=True parameter on the coverage() constructor. The module-level interface still uses automatic saving.
  • Code in the Python standard library is not measured by default. If you need to measure standard library code, use the -L command-line switch during execution, or the cover_pylib=True argument to the coverage() constructor.
  • API changes:
    • Added parameters to coverage.__init__ for options that had been set on the coverage object itself.
    • Added clear_exclude() and get_exclude_list() methods for programmatic manipulation of the exclude regexes.
    • Added coverage.load() to read previously-saved data from the data file.
    • coverage.annotate_file is no longer available.
    • Removed the undocumented cache_file argument to coverage.usecache().