import os
from setuptools import setup
from setuptools.command.install import install

class CustomInstallCommand(install):
    def run(self):
        install.run(self)
        # Run the post-install script
        os.system('python post_install.py')

requirement_path = "requirements.txt"
install_requires = []
if os.path.isfile(requirement_path):
    with open(requirement_path) as f:
        install_requires = f.read().splitlines()

setup(
    name="mypackage",
    install_requires=install_requires,
    cmdclass={
        'install': CustomInstallCommand,
    },
    # ... other setup options ...
)