Getting Started

We’re pleased that you are interested in working on pip.

This document is meant to get you setup to work on pip and to act as a guide and reference to the development setup. If you face any issues during this process, please open an issue about it on the issue tracker.

Get the source code

To work on pip, you first need to get the source code of pip. The source code is available on GitHub.

$ git clone
$ cd pip

Development Environment

pip is a command line application written in Python. For developing pip, you should install Python on your computer.

For developing pip, you need to install nox. The full development setup would then be:

python -m venv .venv
source .venv/bin/activate
python -m pip install nox
py -m venv .venv
py -m pip install nox

Running pip From Source Tree

To run the pip executable from your source tree during development, install pip locally using editable installation (inside a virtualenv). You can then invoke your local source tree pip normally (be sure virtualenv is active).

python -m pip install -e .
python -m pip --version
py -m pip install -e .
py -m pip --version

Running Tests

pip’s tests are written using the pytest test framework and unittest.mock. nox is used to automate the setup and execution of pip’s tests.

It is preferable to run the tests in parallel for a better experience during development, since the tests can take a long time to finish when run sequentially.

To run tests:

$ nox -s test-3.10 -- -n auto

To run tests without parallelization, run:

$ nox -s test-3.10

The example above runs tests against Python 3.10. You can also use other versions like 3.9 and pypy3.

nox has been configured to forward any additional arguments it is given to pytest. This enables the use of pytest’s rich CLI. As an example, you can select tests using the various ways that pytest provides:

$ # Using file name
$ nox -s test-3.10 -- tests/functional/
$ # Using markers
$ nox -s test-3.10 -- -m unit
$ # Using keywords
$ nox -s test-3.10 -- -k "install and not wheel"


When running pip’s tests with OS distribution Python versions, be aware that some functional tests may fail due to potential patches introduced by the distribution. For all tests to pass consider:

  • Installing Python from or compile from source

  • Or, using pyenv to assist with source compilation

Running pip’s entire test suite requires supported version control tools (subversion, bazaar, git, and mercurial) to be installed. If you are missing any of these VCS, those tests should be skipped automatically. You can also explicitly tell pytest to skip those tests:

$ nox -s test-3.10 -- -k "not svn"
$ nox -s test-3.10 -- -k "not (svn or git)"

Running Linters

pip uses pre-commit for managing linting of the codebase. pre-commit performs various checks on all files in pip and uses tools that help follow a consistent code style within the codebase.

To use linters locally, run:

$ nox -s lint


Avoid using # noqa comments to suppress linter warnings - wherever possible, warnings should be fixed instead. # noqa comments are reserved for rare cases where the recommended style causes severe readability problems.

Running pip under a debugger

In order to debug pip’s behavior, you can run it under a debugger like so:

$ python -m pdb -m pip --debug ...

Replace the ... with arguments you’d like to run pip with. Give PDB the c (“continue”) command afterwards, to run the process.

The --debug flag disables pip’s exception handler, which would normally catch all unhandled exceptions. With this flag, pip will let these exceptions propagate outside of its main subroutine, letting them get caught by the debugger. This way you’ll be able to debug an exception post-mortem via PDB.

Building Documentation

pip’s documentation is built using Sphinx. The documentation is written in reStructuredText.

To build it locally, run:

$ nox -s docs

The built documentation can be found in the docs/build folder.

For each Pull Request made the documentation is deployed following this link:


What Next?

The following pages may be helpful for new contributors on where to look next in order to start contributing.