> What do you mean by reverse? You can certainly upgrade all packages locally and then run pip freeze again if you want to set up newer versions, or like manually change versions in your requirements.txt and `pip install --upgrade` to update them. For stronger reproducibility guarantees there's also `--require-hashes`, although admittedly freeze doesn't appear to support easily writing hashes to a requirements.txt.

You need to know, and maintain, both what you intended to depend on and what you physically ended up depending on. So in more sensible ecosystems you will have, e.g., Gemfile and Gemfile.lock. pip freeze is, effectively, the way you create Gemfile.lock, but it forces you to destroy Gemfile to do it. And so you can't really use it.