Creating a new Distutils command

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Now, if you’ve ever used setuptools or pip before, you know how powerful and convenient they can be for managing packages and dependencies. But what if you want to add some extra functionality to the process? That’s where our trusty friend distutils comes in!

For those who are new to this whole setup thing, let me explain: distutils is a set of Python modules that help you build and distribute your own software packages. It provides various tools for creating installers, generating documentation, and handling dependencies. And the best part? You can customize it to suit your needs!

So how do we create our very own distutils command? Well, first things first let’s start with a simple example. Let’s say you want to add a new option that allows users to specify a custom install location for your package. Here’s what the code might look like:

# Importing necessary modules
from setuptools import setup # Importing the setup function from the setuptools module
import os # Importing the os module for operating system related functions

# Setting up the package information
setup(
    name='my_package', # Name of the package
    version='1.0', # Version number of the package
    author='Your Name', # Author of the package
    description='A simple Python package with some cool features!', # Description of the package
    install_requires=['numpy'], # List of dependencies required for the package to function
    packages=['mypackage'], # List of packages to be included in the distribution
    cmdclass={'install': CustomInstallCommand} # Custom command to be executed during installation
)

# Note: The setup function takes in various arguments to configure the package, such as name, version, author, etc. 
# The cmdclass argument allows us to add custom commands to be executed during installation.

# Defining a custom command for installation
class CustomInstallCommand(Command):
    """Custom command for installation"""
    
    # Initializing the command
    def initialize_options(self):
        pass # No options to be initialized
    
    # Running the command
    def run(self):
        # Code to be executed during installation
        # This could include creating directories, copying files, etc.
        pass
    
    # Finalizing the command
    def finalize_options(self):
        pass # No options to be finalized

# Note: The CustomInstallCommand class inherits from the Command class, which is a base class for all distutils commands.
# The initialize_options, run, and finalize_options methods are required to be defined for any custom command. 
# These methods can be used to perform specific tasks during the installation process.

In this example, we’re using setuptools to create a setup script for our package. We’ve added some basic information like the name, version, author, and description. Then we’ve specified that our package requires numpy as a dependency (which is installed automatically when someone installs our package). Finally, we’ve defined a custom command called `install` which will be executed during the installation process.

Now let’s take a closer look at this `CustomInstallCommand`. This class inherits from the built-in `setuptools.command.install` and overrides its functionality to add our own logic:

# This class defines a custom command called `install` which will be executed during the installation process.
class CustomInstallCommand(setuptools.command.install):
    # This method overrides the functionality of the built-in `setuptools.command.install` class.
    def run(self):
        # Call the original install method
        super().run()
        
        # Get the custom installation directory from user input
        custom_dir = input("Enter a custom installation directory: ")
        
        # Set up the new path for our package
        os.environ['PKG_CONFIG'] = f"{custom_dir}/lib/pkgconfig"
        
        # This method installs the data files to the specified output directory.
        self.install_data(self.get_output_directory())

In this code, we’re first calling the original `run()` method from the parent class (which handles most of the installation logic). Then we prompt the user to enter a custom install directory and store it in a variable called `custom_dir`. Next, we set up the new path for our package by modifying the PKG_CONFIG environment variable. Finally, we call the `install_data()` method which copies any data files (like documentation or examples) into their appropriate locations.

And that’s it! Now when someone installs your package using pip or setuptools, they will be prompted to enter a custom installation directory. This can come in handy if you want to avoid cluttering up the default system directories with unnecessary files and dependencies. Plus, it adds an extra layer of flexibility for users who prefer to have more control over their installations!

Of course, this is just one example there are countless other ways to customize distutils commands depending on your needs. But hopefully this gives you a good starting point for exploring the possibilities!

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