How to continue in nested loops in Python

Question

How can you continue the parent loop of say two nested loops in Python?

for a in b:
    for c in d:
        for e in f:
            if somecondition:
                <continue the for a in b loop?>

I know you can avoid this in the majority of cases but can it be done in Python?

Answer 1

You use break to break out of the inner loop and continue with the parent

for a in b:
    for c in d:
        if somecondition:
            break # go back to parent loop

Answer 2

use a boolean flag

problem = False
for a in b:
  for c in d:
    if problem:
      continue
    for e in f:
        if somecondition:
            problem = True

Answer 3

Here's a bunch of hacky ways to do it:

1. Create a local function

   for a in b:
       def doWork():
           for c in d:
               for e in f:
                   if somecondition:
                       return # <continue the for a in b loop?>
       doWork()
   

   A better option would be to move doWork somewhere else and pass its state as arguments.

2. Use an exception

   class StopLookingForThings(Exception): pass
   
   for a in b:
       try:
           for c in d:
               for e in f:
                   if somecondition:
                       raise StopLookingForThings()
       except StopLookingForThings:
           pass
   

Answer 4

from itertools import product
for a in b:
    for c, e in product(d, f):
        if somecondition:
            break

Answer 5

1. Break from the inner loop (if there's nothing else after it)
2. Put the outer loop's body in a function and return from the function
3. Raise an exception and catch it at the outer level
4. Set a flag, break from the inner loop and test it at an outer level.
5. Refactor the code so you no longer have to do this.

I would go with 5 every time.