Pythonista uses Python 2.7.5, which is a little older than the current 2.7.11 (and I think 2.7.12 is currently in release candidate status). So any standard library features added after 2.7.5 aren't available in Pythonista.
Welcome!
This is the community forum for my apps Pythonista and Editorial.
For individual support questions, you can also send an email. If you have a very short question or just want to say hello — I'm @olemoritz on Twitter.