breaking outof nexted loops

[Skaperen]

one of the many coding difficulties i encounter in most languages is breaking out of 2 or more nested loops. in C i did have a goto but that was considered bad code. i do recall there was a language that allowed break to have a number (always must be a hard coded literal constant) to specify the number of loop levels to break out of. the usual way is to break out of each level one at a time based on a specific variable or specific value(s). constrained types like bytearray can sometimes force an extra variable.

what coding techniques to do things like this have you come up with?

[buran]

Can you refactor your code to use single loop to iterate over itertools.product instead of having nested loops?

[perfringo]

Suggested practice is the use of 'return': Guido rejecting PEP 3136 -- Labeled break and continue.

Of course one can break out of nested loop but this is not something which is easy to understand - using for-loop with else and then break:

for loop:                 # outer loop
    # do something
    for loop:             # inner loop
        # do something
        # outcome: break or no-break
    else:                 # no-break
        continue          # go back to outer loop
    break                 # break occured in inner loop, break outer loop as well
 

[Gribouillis]

what coding techniques to do things like this have you come up with?

A simple way to exit a deeply nested loop in python is to raise an exception. In fact I once wrote a thread in this forum with a 'context' specially designed to exit deeply nested loops, even across functions boundaries. It remains a case study, because I don't use it in practice.

[Skaperen]

i could use return if the context change could be dealt with. i do like the idea of exceptions but i think refactoring to use itertools.product would be best for cases where that can be done.