Dynamic package installation depend upon the specific system using setup.py install_requires

Question

I have a setup.py as below configuration

setup(
install_requires = ['django == 2.0']
)

I would like to modify the setup.py based on docker usage.

If user uses docker then the configuration must be

setup(
install_requires = ['django == 4.0']
)

else

setup(
install_requires = ['django == 2.0']
)

I have tried using environement variable but not working.

if 'ENV_VAR' in os.environ:
  django = ['django == 4.0']
else:
 django = ['django == 2.0']

setup(
install_requires = django
)