How to handle exceptions in a list comprehensions?

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I realize this question is quite old, but you can also create a general function to make this kind of thing easier:

def catch(func, handle=lambda e : e, *args, **kwargs):
    try:
        return func(*args, **kwargs)
    except Exception as e:
        return handle(e)

Then, in your comprehension:

eggs = (1,3,0,3,2)
[catch(lambda : 1/egg) for egg in eggs]
[1, 0, ('integer division or modulo by zero'), 0, 0]

You can of course make the default handle function whatever you want (say you’d rather return ‘None’ by default).

Hope this helps you or any future viewers of this question!

Note: in python 3, I would make the ‘handle’ argument keyword only, and put it at the end of the argument list. This would make actually passing arguments and such through catch much more natural.

Update (9 years later…): For Python 3, I just meant switch *args and handle, so you can specify arguments to the function without specifying handle. A minor convenience:

def catch(func, *args, handle=lambda e : e, **kwargs):
    try:
        return func(*args, **kwargs)
    except Exception as e:
        return handle(e)

This is helpful when using a defined function in the comprehension:

from math import log    
eggs = [1,3,0,3,2]
[catch(log, egg) for egg in eggs]
[0.0, 1.0986122886681098, ValueError('math domain error'), 1.0986122886681098, 0.6931471805599453]

Under the Python 2 version, we would’ve had to pass in handle before the egg.

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