How to restart for loop in python?

Question

This might not be possible but if it is, I want to know how can it be done?

Here is my code-structure

for item in somelist:
    # Calcuating some stuff

inside my for loop, I have some evaluation to do which might cause exception.
and even if I handle the exception, current iteration is passed as in complete
What I want to do is, if I get exception, I want to re-evaluate current iteration with some new information.
Is it possible?
Example

for item in somelist:
    try:
        # calculating item
    except Exception:
        # re-running current iteration (not from the beginning)

Might want to take care - if re-evaluation results in another exception ... and so on ... you could end up with an infinite loop. — topsail
– topsail, Commented Jun 6, 2022 at 15:45
Not possible. The for loop uses the iterator protocol, which means the only thing it can do (after using iter(somelist) to get the iterator in the first place) is call next on that iterator. — chepner
– chepner, Commented Jun 6, 2022 at 15:47
What you can do is put another loop in the body of the for loop which doesn't exit until you are finally done with item and ready to get the next value. — chepner
– chepner, Commented Jun 6, 2022 at 15:47

Samwise · Accepted Answer · 2022-06-06 15:47:45Z

3

I'd suggest using an inner loop to handle the retry:

for item in somelist:
    while True:
        try:
            # calculating item
            break  # breaks inner loop, outer loop continues
        except Exception:
            # get new information, inner loop continues implicitly

If you want to retry a limited number of times to avoid the possibility of an infinite loop, that's easily accomplished by making the inner loop something like for _ in range(NUM_RETRIES).

answered Jun 6, 2022 at 15:47

Samwise

72.1k3 gold badges36 silver badges52 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

SCcagg5 · Accepted Answer · 2022-06-06 15:44:15Z

1

If you're using a list try using while instead of for loop

i = 0
while i < len(somelist):
  item = somelist[i]
  try:
        # calculating item
  except Exception:
    i -= 1
  i += 1

answered Jun 6, 2022 at 15:44

SCcagg5

6585 silver badges17 bronze badges

Collectives™ on Stack Overflow

How to restart for loop in python?

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related