>Why didn't they just use a single global loop? Sorta like javascript and golang.

I imagine the problem is, that neither JS or Golang have to deal with, is Python supports plain old threads. If you have a single global event loop, and then you try execute a future what should happen?

1. Should every every thread have its own loop? Then how would you send futures to another thread.

2. Should the global loop only exist on a single thread? Then you would have to pay a synchronization tax every time you pushed a task to the loop.

Not saying the Python solution is 100% right (I've only thought about it for 5 minutes), but I can see how being compatible with threads has caused this situation. I believe the default now is you don't have to think about loops, and Python does the right thing for 99% of use cases.