如何从它的 try catch 块内部中断 for 循环？

Question

I'm trying to find a way to get out of this for loop if the code block inside the try except block (inside the for loop) is succesfully executed , and not calling the exception.

Here's the code which doesn't work for me :

attempts = ['I15', 'J15']
for attempt in attempts:
    try:
        avar = afunc(attempt)
        break
    except KeyError:
        pass
        if attempt == attempts[-1]:
            raise KeyError

Because it's still calling the J15 item inside the attempts list after the I15 is succesfully executed

The code here :

    except KeyError:
        pass
        if attempt == attempts[-1]:
            raise KeyError

Is used to throw the actual exception if the code already tried the whole attempt in attempts

Answer 1

You need the for … else concept: https://docs.python.org/3/tutorial/controlflow.html#break-and-continue-statements-and-else-clauses-on-loops

attempts = ['I15', 'J15']
for attempt in attempts:
    try:
        avar = afunc(attempt)
    except KeyError:
        # error, let's try another item from attempts
        continue
    else:
        # success, let's get out of the loop
        break
else:
    # this happens at the end of the loop if there is no break
    raise KeyError

Answer 2

I believe the cleanest way will be to continue inside the except block, and break ing just after it. In this case you don't even have to use avar (unless I misunderstood the question).

attempts = ['I15', 'J15']
for attempt in attempts:
    try:
        afunc(attempt)
    except KeyError:
        continue
    break

If you do need avar for a later usage:

attempts = ['I15', 'J15']
for attempt in attempts:
    try:
        avar = afunc(attempt)
    except KeyError:
        continue
    break
print(avar) # avar is a available here, as long as at least one attempt was successful