When it comes to shipping Python server-side apps, Pipenv is a godsend. Before discovering it, I had 3 requirements.txt files (common, dev, prod) which I had to edit manually. This often meant forgetting to include something that I just installed and only finding out after a full round of QA. It also meant a separate couple of steps for full-tree dependency freezing which never worked quite properly anyways. Pipenv just....works. Dependencies are saved as I install them, I only have to deal with the top-level ones, but the whole tree is locked.