<s>[INST] Upgrading all packages with pip Is it possible to upgrade all Python packages at one time with pip?
Note that there is a feature request for this on the official issue tracker.
 [/INST] There isn't a built-in flag yet, but you can use
pip freeze --local | grep -v '^\-e' | cut -d = -f 1  | xargs -n1 pip install -U

Note: there are infinite potential variations for this. I'm trying to keep this answer short and simple, but please do suggest variations in the comments!
Relevant edits:

Added a grep to skip "-e" package definitions, as suggested by @jawache (Yes, you could replace grep+cut with sed or awk or Perl or...).
Newer versions of pip allow you to list outdated packages, though not in "requirements" format: pip list --outdated
Added -n1 to xargs, prevents stopping everything if updating one package fails (thanks @andsens)

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