Messages

Coverage.py has a number of messages for conditions that could affect measurement or reporting.

Errors

No source for code: ‘filename.py’

A source file was traced during execution, but was not found when trying to produce a report. Often this is due to libraries creating temporary source files which are deleted after execution.

You can add configuration settings to avoid the error:

  • Use “[run] source=.” to prevent measurement of code outside of your project.

  • Use “[report] omit=$TMPDIR/*” to explicitly skip reporting the temporary directory where the files were created. The appropriate environment variable will depend on your system.

  • Use “[report] ignore_errors = true” to treat the error as a warning.

Can’t combine (branch or statement) coverage data with (statement or branch) data

You have some data files that measured branch coverage and some data files that didn’t. They cannot be combined because the two types of data are incompatible. You’ll need to ensure that all of your data files are collected with the same settings.

Warnings

Warnings are issued for possible problems but don’t stop the measurement or reporting. See below for the details of each warning, and how to suppress warnings you don’t need to see.

Couldn’t parse Python file XXX (couldnt-parse)

During reporting, a file was thought to be Python, but it couldn’t be parsed as Python.

Trace function changed, data is likely wrong: XXX (trace-changed)

Coverage measurement depends on a Python setting called the trace function. Other Python code in your product might change that function, which will disrupt coverage.py’s measurement. This warning indicates that has happened. The XXX in the message is the new trace function value, which might provide a clue to the cause.

Module XXX has no Python source (module-not-python)

You asked coverage.py to measure module XXX, but once it was imported, it turned out not to have a corresponding .py file. Without a .py file, coverage.py can’t report on missing lines.

Module XXX was never imported (module-not-imported)

You asked coverage.py to measure module XXX, but it was never imported by your program.

No data was collected (no-data-collected)

Coverage.py ran your program, but didn’t measure any lines as executed. This could be because you asked to measure only modules that never ran, or for other reasons.

To debug this problem, try using run --debug=trace to see the tracing decision made for each file.

Module XXX was previously imported, but not measured (module-not-measured)

You asked coverage.py to measure module XXX, but it had already been imported when coverage started. This meant coverage.py couldn’t monitor its execution.

Already imported a file that will be measured: XXX (already-imported)

File XXX had already been imported when coverage.py started measurement. Your setting for --source or --include indicates that you wanted to measure that file. Lines will be missing from the coverage report since the execution during import hadn’t been measured.

--include is ignored because --source is set (include-ignored)

Both --include and --source were specified while running code. Both are meant to focus measurement on a particular part of your source code, so --include is ignored in favor of --source.

Conflicting dynamic contexts (dynamic-conflict)

The [run] dynamic_context option is set in the configuration file, but something (probably a test runner plugin) is also calling the Coverage.switch_context() function to change the context. Only one of these mechanisms should be in use at a time.

Couldn’t import C tracer (no-ctracer)

The core tracer implemented in C should have been used, but couldn’t be imported. The reason is included in the warning message. The Python tracer will be used instead.

Can’t use core=sysmon: sys.monitoring isn’t available in this version, using default core (no-sysmon)

You requested to the sys.monitoring measurement core, but are running on Python 3.11 or lower where it isn’t available. A default core will be used instead.

Can’t use core=sysmon: sys.monitoring can’t measure branches in this version, using default core (no-sysmon)

You requested the sys.monitoring measurement core and also branch coverage. This isn’t supported until Python 3.14. A default core will be used instead.

Can’t use core=sysmon: it doesn’t yet support dynamic contexts, using default core (no-sysmon)

You requested the sys.monitoring measurement core and also dynamic contexts. This isn’t supported by coverage.py yet. A default core will be used instead.

Can’t use core=sysmon: it doesn’t support concurrency=ZZZ, using default core (no-sysmon)

Your requested the sys.monitoring measurement core and also a particular concurrency setting, but that combination isn’t supported. A default core will be used instead.

Disabling warnings

Individual warnings can be disabled with the disable_warnings configuration setting. It is a list of the short parenthetical nicknames in the warning messages. For example, to silence “No data was collected (no-data-collected)”, add this to your configuration file:

  • pyproject.toml
  • .coveragerc
  • .coveragerc.toml
  • setup.cfg or tox.ini
[tool.coverage.run]
disable_warnings = ["no-data-collected"]

[run]
disable_warnings = no-data-collected

# You can also use sections like [tool.coverage.run]
[run]
disable_warnings = ["no-data-collected"]

[coverage:run]
disable_warnings = no-data-collected