It is because only one thread at a time holds the lock in order to avoid race conditions. The keynote[1] by Raymond Hettinger from PyBay '17 will be a great pla

It is because only one thread at a time holds the lock in order to avoid race conditions. The keynote[1] by Raymond Hettinger from PyBay '17 will be a great place to start if you are new to this. [1] https://youtu.be/9zinZmE3Ogk https://youtu.be/9zinZmE3Ogk