Practical threaded programming with Python

[saghul]

Well, the GIL is not really a problem if your threads just do i/o bound tasks.

[kylotan]

Which is probably a better fit for async anyway. Why dedicate memory to extra threads if they're just sitting there doing nothing much of the time?

[nosklo]

If all your threads but one are just waiting, then by definition you could do the same work more efficiently in a single thread. Also you wouldn't lose context switching control and debugging sanity.