I would recommend avoiding Pythonista myself as it is abandonware but that has been possible for a long time via stash which is still actively developed https://github.com/ywangd/stash
there are a few other python environments that support pip install
It used to be so good five or so years ago, I remember being so excited about it and even writing so nice little scripts in it. It's sad that it's in the state it is now
Sirened|3 years ago