[Tutor] casting string to integer in a list of lists

[wesley chun]

>> except:
>>    pass
>>
>> try not to code these 2 lines in anything that you do because it will
>> come back to haunt you when something is not working right but you
>> can't find any errors. that's because this code masks and throws away
>> everything!!
>
> there are two potential error types: IndexError and ValueError.  I assumed that if
> either one occurred, we would want to leave that particular list member (if
> it exists) as-is (hence the pass).
>        :
> - catch the exception, test to see whether it's an IndexError or a
> ValueError, and if not then do something;
>        :

as opposed to the above...

except (IndexError, ValueError):
    pass

...is much more acceptable. there are 2 general conventions:

- catch errors explicitly (as to not mask the others) and pass/ignore
- catch 'em all (except Exception) and do *some*thing (not pass)

both of those cases shows that you did your due diligence and that
you're just not blindly throwing things away.


> Generally, if there are two or more "acceptable" errors that you can foresee,
> but you still want to catch any others, what's an elegant, readable,  and
> computationally-cheap way to do it?  Maybe a dictionary of exceptions...?

A tuple of exceptions works, just like what we did above, and more,
i.e., (IndexError, ValueError, TypeError, KeyError...

hope this helps!
-- wesley
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
"Core Python Programming", Prentice Hall, (c)2007,2001
"Python Fundamentals", Prentice Hall, (c)2009
    http://corepython.com

wesley.j.chun :: wescpy-at-gmail.com
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cyberweb.consulting : silicon valley, ca
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