[throwaway892238]

A Makefile makes this trivial:

  # Makefile
  all: venv frozen test
  
  venv:
   python3 -m venv install venv
  
  frozen:
   [ -e frozen.txt ] || { echo "ERROR: run 'make update-frozen'"; exit 1 ; }
   ./venv/bin/pip install -r frozen.txt
  
  update-frozen: clean install-requirements freeze
  
  freeze:
   ./venv/bin/pip freeze > frozen.txt
  
  install-requirements:
   [ -e requirements.txt ] || { echo "ERROR: make a requirements.txt file"; exit 1 ; }
   ./venv/bin/pip install -r requirements.txt
  
  test:
   ./venv/bin/python3 run_tests.py
  
  clean:
   rm -rf venv

Put your package names in requirements.txt and run `make update-frozen`. To reinstall everything from frozen state, `make clean frozen`. (And replace the first space with a tab; HN is stripping my tabs out)

I know Pythonistas like to use Python for everything, but there are other tools out there that will make your life much simpler.