Are you talking about importing modules that exist in Python’s Standard Library? You can import many modules that exist in Python’s Standard Library.
Here’s some documentation about the modules you can import using Jython 2.5:
jython.org/docs/library/indexprogress.html
If you are talking about third-party Python libraries, you can copy and paste code from a third-party Python library into Ignition app modules. You will likely need to make scoping changes and change some names to use app.* module names.
In some cases this can be done and work. I’ve seen it work a couple times.
Kyle is right that Ignition 7.7 will have a better way to add third-party Python libraries to Ignition.