except clause syntax question

Mel Wilson mwilson at the-wire.com
Mon Jan 30 14:15:04 EST 2012

Charles Yeomans wrote:

> To catch more than one exception type in an except block, one writes
> except (A, B, C) as e:
> I'm wondering why it was decided to match tuples, but not lists:
> except [A, B, C] as e:
> The latter makes more sense semantically to me -- "catch all exception
> types in a list" as opposed to "catch this single thing composed of three
> exception types".

I've always been perfectly fine with sometimes treating tuples as immutable 
sequences, so I'm +0 on saying "more sense semantically", but given that the 
exception list can be a variable, I'm not sure what the gain is by keeping 
it immutable.

#!/usr/bin/env python
# -*- coding: ASCII -*-
'''Demonstrate catching variable exceptions.
def excepter (a, exceptions):
        'Number ' + a
    except exceptions as e:
        print '!!! *** EXCEPTER CAUGHT ONE *** !!!'
        print repr (e)
#~ excepter (0, [ZeroDivisionError])
excepter (0, (ZeroDivisionError,))
excepter (1, (ZeroDivisionError,TypeError))
excepter (1, (ZeroDivisionError,))


excepter called with the list catches nothing, of course.


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