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PEX

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.. contents:: Contents

Overview

pex is a library for generating .pex (Python EXecutable) files which are executable Python environments in the spirit of virtualenvs <https://virtualenv.pypa.io>. pex is an expansion upon the ideas outlined in PEP 441 <https://peps.python.org/pep-0441/> 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 <http://pantsbuild.org/>, Buck <http://facebook.github.io/buck/>, and {py}gradle <https://github.com/linkedin/pygradle>_ also support building .pex files directly.

Still unsure about what pex does or how it works? Watch this quick lightning talk: WTF is PEX? <https://www.youtube.com/watch?v=NmpnGhRwsu0>_.

pex is licensed under the Apache2 license.

Installation

To install pex, simply

.. code-block:: bash

$ pip install pex

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

.. code-block:: bash

$ 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.

Simple Examples

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

.. code-block:: bash

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

Save Dependencies From Pip

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

.. code-block:: bash

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

Ephemeral Environments
~~~~~~~~~~~~~~~~~~~~~~

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

.. code-block:: bash

    $ pex flask -- webserver.py

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

.. code-block:: bash

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

Using Entry Points
~~~~~~~~~~~~~~~~~~

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:

.. code-block:: bash

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

Specifying A Specific Interpreter

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

.. code-block:: bash

$ 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.

Documentation

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

Development

Pex uses uv <https://docs.astral.sh/uv/>_ with dev-cmd <https://pypi.org/project/dev-cmd/>_ for test and development automation. After you have installed uv, to run the Pex test suite, just run dev-cmd via uv:

.. code-block:: bash

$ 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:

.. code-block::

$ 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:

.. code-block::

$ uvrc typecheck

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

.. code-block::

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

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

.. code-block::

$ python -m pex