This is a summary out of the documents I have read through about these related topics. I didn't take the time to dig in Python's source code, so some conclusions are just conjectures. Threads interact ...

See Future Objects for more information abaout it. This decorator doesn't affect to thread safty, so it depends only on the invoked callable whether the decorated will be thread safe or not.

However, Python 3.5 added a new feature called 'asyncio', which, when used correctly, can be excellent for writing efficient IO-bound code.