Python: Continuing to next iteration in outer loop

Question

Hi,

I wanted to know if there are any built-in ways to continue to next iteration in outer loop in python. For example, consider the code:

for ii in range(200):
    for jj in range(200, 400):
        ...block0...
        if something:
            continue
    ...block1...

I want this continue statement to exit the jj loop and goto next item in the ii loop. I can implement this logic in someother way (by setting a flag variable), but is there an easy way to do this, or is this like asking for too much?

Thanks

Answer 1

for ii in range(200):
    for jj in range(200, 400):
        ...block0...
        if something:
            break
    else:
        ...block1...

Break will break the inner loop, and block1 won't be executed (it will run only if the inner loop is exited normally).

Answer 2

In other languages you can label the loop and break from the labelled loop. Python Enhancement Proposal (PEP) 3136 suggested adding these to Python but Guido rejected it:

However, I'm rejecting it on the basis that code so complicated to require this feature is very rare. In most cases there are existing work-arounds that produce clean code, for example using 'return'. While I'm sure there are some (rare) real cases where clarity of the code would suffer from a refactoring that makes it possible to use return, this is offset by two issues:

1. The complexity added to the language, permanently. This affects not only all Python implementations, but also every source analysis tool, plus of course all documentation for the language.

2. My expectation that the feature will be abused more than it will be used right, leading to a net decrease in code clarity (measured across all Python code written henceforth). Lazy programmers are everywhere, and before you know it you have an incredible mess on your hands of unintelligible code.

So if that's what you were hoping for you're out of luck, but look at one of the other answers as there are good options there.

Answer 3

I think you could do something like this:

for ii in range(200):
    restart = False
    for jj in range(200, 400):
        ...block0...
        if something:
            restart = True
            break
    if restart:
        continue
    ...block1...