Coverage.py

What it does

Branch coverage

The tool can measure whether alternative branch paths were executed.checked 15 Oct 2026

C extension

A C extension is recommended for speed and is required for concurrency and plugin features; Linux builds may need development headers and GCC.checked 15 Oct 2026

Configuration

Settings can live in .coveragerc, TOML, setup.cfg, tox.ini, or pyproject.toml files.checked 15 Oct 2026

Contexts

Dynamic contexts can record which test function ran which lines of code.checked 3 Oct 2026

Coverage data API

`CoverageData` provides a supported interface for reading collected coverage data.checked 15 Oct 2026

Coverage types

It measures statement coverage by default and can also measure branch coverage.checked 3 Oct 2026

Database format

Collected results are stored in a SQLite database, whose schema is documented as advanced and subject to change.checked 15 Oct 2026

Documentation and support

Help is offered through extensive Read the Docs material, Python forums, Python Discord, GitHub issues, and optional Tidelift support.checked 15 Oct 2026

Extensibility

Third-party plugins can extend measurement to non-Python files, such as mapping executed Python back to Django HTML templates.checked 3 Oct 2026

Installation

The documented installation command is `python3 -m pip install coverage`.checked 15 Oct 2026

Integrations

Official examples cover pytest, unittest, and nose, and pytest commonly uses the pytest-cov plugin.checked 15 Oct 2026

Intended users

The documentation presents Coverage.py as a tool for people measuring Python test effectiveness by seeing which code tests exercise and which they miss.checked 3 Oct 2026

Licence

The package is distributed under the Apache 2.0 licence.checked 15 Oct 2026

License

Coverage.py is licensed under the Apache 2.0 License.checked 3 Oct 2026

Limit: default test distinction

ClickUp notes that Coverage.py does not automatically distinguish test code from the application code being tested.checked 15 Oct 2026

Limit: dynamic execution

Hysen Labs cautions that dynamically generated code using exec or eval may not be captured accurately.checked 15 Oct 2026

Limit: language scope

Independent reviews identify Python as the supported product language, limiting use for multi-language coverage programs.checked 15 Oct 2026

Limit: measured performance

A 2023 arXiv study measured median overhead of 180% on CPython and 1,300% on PyPy for coverage.py.checked 15 Oct 2026

Limit: test-quality signal

Pythonlib notes that execution coverage shows whether code ran but cannot determine whether tests assert correct outcomes.checked 15 Oct 2026

Limit: tracing overhead

Hysen Labs warns that tracing every executed line can noticeably slow large test suites.checked 15 Oct 2026

Maintainer and adoption

Batchelder's résumé describes him as solo maintainer since 2004 and reports use by about 34,000 PyPI packages, 65 million monthly downloads, and 365,000 GitHub repositories.checked 15 Oct 2026

Maintainer history

Ned Batchelder has extended and maintained the project since 2004.checked 15 Oct 2026

Measurement cores

Coverage.py offers ctrace and pytrace tracing cores plus a sysmon core; sysmon is faster for simple line and branch coverage but does not yet support dynamic contexts or plugins.checked 3 Oct 2026

Notable organization change

A November 2025 post announced moving the repository to the coveragepy GitHub organization and described the project as essentially a one-person effort.checked 15 Oct 2026