list system and pip-installed modules available to the current python context

list_available_modules.py

import sys as s
for m in s.modules.values():
    if hasattr(m, '__file__'):
        print(m.__file__)
    else:
        print(m)

import pip
for p in pip.get_installed_distributions():
    if hasattr(p, 'location'):
        print(p.location + "/" + p.key)
    else:
        print(p)

verify_pythonpath.sh

# install globally
pip install -r requirements.txt 
python < list_available_modules.py

# install to custom path
pip install -r requirements.txt --target .pip; 
PYTHONPATH=.pip:$PYTHONPATH python < list_available_modules.py