Do python thread wait for standard output?

Question

if you run couple of threads but they all have to print to the same stdout, does this mean they have to wait on each other? so say if all 4 threads have something to write, they have to pause and wait for the stdout to be free so they can get on with their work?

Answer 1

Deep deep (deep deep deep...) down in the OS's system calls, yes. Modern OSes have thread-safe terminal printing routines which usually just lock around the critical sections that do the actual device access (or buffer, depending on what you're writing into and what its settings are). These waits are very short, however. Keep in mind that this is IO you're dealing with here, so the wait times are likely to be negligible relatively to actual IO execution.