pex is a library for generating .pex (Python EXecutable) files which are executable Python environments in the spirit of virtualenvs. pex is an expansion upon the ideas outlined in PEP 441 and makes the deployment of Python applications as simple as cp. pex files may even include multiple platform-specific Python distributions, meaning that a single pex file can be portable across Linux and OS X.

pex files can be built using the pex tool. Build systems such as Pants, Buck, and {py}gradle also support building .pex files directly.

Still unsure about what pex does or how it works? Watch this quick lightning talk: WTF is PEX?.

pex is licensed under the Apache2 license.

To install pex, simply

$ pip install pex

You can also build pex in a git clone using uv:

$ uv run dev-cmd package
$ cp dist/pex ~/bin

This builds a pex binary in dist/pex that can be copied onto your $PATH. The advantage to this approach is that it keeps your Python environment as empty as possible and is more in-line with what pex does philosophically.

Launch an interpreter with requests, flask and psutil in the environment:

$ pex requests flask 'psutil>2,<3'

Or instead freeze your current virtualenv via requirements.txt and execute it anywhere:

$ pex $(pip freeze) -o my_virtualenv.pex
$ deactivate
$ ./my_virtualenv.pex

Run webserver.py in an environment containing flask as a quick way to experiment:

$ pex flask -- webserver.py

Launch Sphinx in an ephemeral pex environment using the Sphinx entry point sphinx:main:

$ pex sphinx -e sphinx:main -- --help

Projects specifying a console_scripts entry point in their configuration can build standalone executables for those entry points.

To build a standalone pex-tools-executable.pex binary that runs the pex-tools console script found in all pex version 2.1.35 and newer distributions:

$ pex "pex>=2.1.35" --console-script pex-tools --output-file pex-tools-executable.pex

You can also build pex files that use a specific interpreter type:

$ pex "pex>=2.1.35" -c pex-tools --python=pypy -o pex-tools-pypy-executable.pex

Most pex options compose well with one another, so the above commands can be mixed and matched, and equivalent short options are available.

For a full list of options, just type pex --help.

More documentation about Pex, building .pex files, and how .pex files work is available at https://docs.pex-tool.org.

Pex uses uv with dev-cmd for test and development automation. After you have installed uv, to run the Pex test suite, just run dev-cmd via uv:

$ uv run dev-cmd

The dev-cmd command runner provides many useful options, explained at https://pypi.org/project/dev-cmd/ . Below, we provide some of the most commonly used commands when working on Pex, but the docs are worth acquainting yourself with to better understand how dev-cmd works and how to execute more advanced work flows.

To run a specific command, identify the name of the command you'd like to invoke by running uv run dev-cmd --list, then invoke the command by name like this:

$ uv run dev-cmd format

That's a fair bit of typing. An shell alias is recommended, and the standard is uvrc which I'll use from here on out.

To run MyPy:

$ uvrc typecheck

All of our tests allow passthrough arguments to pytest, which can be helpful to run specific tests:

$ uvrc test-py37-integration -- -k test_reproducible_build

To run Pex from source, rather than through what is on your PATH, invoke via Python:

$ python -m pex