I copied some code containing a 'while' loop and edited it to remove the loop. In doing so I acidentally left in a 'break' statement.

Running the script did absolutely nothing. No error - it seemed to run and just stop. I tried adding diagnostics - nothing worked. Foxed me for ages! Just add a spurious 'break' into a script to try it.

I suspect a bug in the interpreter, but maybe there's a reason for it. (In IDLE/Linux it throws an error.)