Hello @409686,
There are now two flavours of Python inside Dynamo; one that enables the use of Python 2 (Called “IronPython2”) and has been present in Dynamo since the 1.X days, and another that enables the use of Python 3 (Called “CPython3”) which is available from Dynamo 2.7 onwards.
There are differences between the versions for two primary reasons: One, Python itself is different between Python 2 and Python 3 (Namely, some key syntax changes), and Two, the way within which Python will talk to .NET land (Which Dynamo is primarily build in).
You can learn a little more about it here: https://github.com/DynamoDS/Dynamo/wiki/Work-in-progress-to-improve-Python-3-support
In short, they are different
If you want an in-depth look at IronPython2, then look no further than @oliver.green’s awesome Gitbook on the subject: Learn Python for Dynamo: The Dynamo Python Primer
We don’t have many Python 3 resources out there yet, so I would start with Python 2 as it’s much more well established inside the Dynamo ecosystem.