Because of the sometimes much-maligned Global Interpreter Lock, purePython code itself can't run simultaneously on multiple CPUs. So whatshould you use Python threads for?

The real use for Python threads is turning synchronous functions inextension modules into asynchronous things that don't delay your mainprogram. Often these functions have no asynchronous equivalents (unlikenetwork IO), so it is either use threads or have your main programdelayed. This works for sufficiently compute-intensive functions as wellas functions, like socket.