Python's `setuptools` is a dominant library for packaging Python projects. It extends the standard Python `distutils` with many powerful features, one of which is the ability to run post-install scripts. This functionality can be quite useful for performing additional setup steps after a package installation, such as installing external dependencies, setting environment variables, or configuring settings.

Understanding Post-install Scripts in Setuptools

In `setuptools`, a post-install script is typically executed via the `entry_points` in the `setup.py` file. Entry points are a way of specifying what a package can provide to another package or application. When an entry point is designated as a post-install command, it will automatically run once your package installation is complete.

Creating a Post-install Script

To create a post-install script using `setuptools`, follow these general steps:

1. Define the Post-install Function: This function will encompass the actions you wish to carry out post-installation.
2. Modify `setup.py`: Integrate your function with `setuptools` using `entry_points`.
3. Test the Script: Verify that the script functions as expected after installation.

Step-by-Step Example

1. Define the Post-install Function

Start by defining a post-install function. This function will contain the logic you wish to execute post-installation. Create a Python module for your scripts if you don't have one already, e.g., `post_install.py`.

• Portability: Ensure scripts are platform-independent whenever possible.
• Dependencies: Avoid using post-install scripts to install dependencies not specified in `install_requires`, as this can lead to an incomplete installation if the script fails.
• Error Handling: Implement robust error handling to prevent the script from crashing on failure, ensuring logging or rollback if necessary.
• PEP 517/518: With the advancements in Python packaging standards like PEP 517 and PEP 518, you might consider moving towards using pyproject.toml for more modern builds. However, note that post-install scripts are still primarily handled at lower levels of packaging that can incorporate `setuptools`.
• Documentation: Ensure any important changes made during post-installation are well-documented, providing users with clear guidance on the actions taken by these scripts.