pex

PEX example

This folder shows examples of how to use the run-pex-as-data-source and run-pex-as-resource modules to run python scripts wrapped with a PEX environment.

These modules use the prepare-pex-environment module under the hood to prepare the runtime environment for unpacking and running PEX binaries. You can learn more about PEX in the module documentation.

The python script

This example will run the python script using the PEX environment provided in the sample-python-script folder. The PEX environment contains a virtualenv with all the requirements specified in requirements.txt installed. The PEX environment only includes the virtualenv and does not include the script. If you run it directly, you will be dropped into a python shell with the PATH set such that you can import the requirements. If you would like to run the script directly, you must call it from the PEX:

python ./sample-python-script/bin/sample_python_script_py27_env.pex ./sample-python-script/sample_python_script/main.py

Note that the PEX is versioned by python version (py27 or py3). The py27 PEX only works with python 2.7, while the py3 PEX will work with python versions 3.5, 3.6, and 3.7.

Building the PEX

The PEX file is created using the pex utility. However, since it is versioned to be compatible with multiple versions of python, you must have each version of python installed. It is recommended to use pyenv to help setup an environment with multiple python interpreters.

For convenience, a build script with a local pyenv version (a .python-version file) is provided. To use the build script, first install all necessary versions of python with pyenv:

pyenv install 2.7.12
pyenv install 3.5.2
pyenv install 3.6.6
pyenv install 3.7.0

Once the python versions are installed, change your working directory to the build_scripts directory:

# From the repo root
cd ./examples/pex/sample-python-script/build_scripts

Finally, run the build script:

./build.sh

This will build the PEX binary files for each python version and put it in the bin directory.

NOTE: Although the build script only supports Unix environments, the PEX that it creates is compatible with Windows environments.

How do you run these examples?

1. Ensure python is installed in your OS.
2. Install Terraform.
3. terraform init.
4. terraform apply.