pip freeze --local | grep -v '^\-e' | cut -d = -f 1 | xargs -n1 pip install -U
J'ai fait un alias dans ~/.bash_aliases :
alias pip-up="pip freeze --local | grep -v '^\-e' | cut -d = -f 1 | xargs -n1 pip install -U"
(Ne pas oublier de relancer source ~/.bashrc).
Source: https://stackoverflow.com/questions/2720014/upgrading-all-packages-with-pip