[Python-ideas] Default return values to int and float

[Jan Kaliszewski]

Steven D'Aprano dixit (2011-10-08, 22:23):

> Ron Adam wrote:
[snip]
> >What if you can catch an exception specifically from a particular
> >function or method, but let other unexpected "like" exceptions bubble
> >through...
> >
> >   try:
> >      ...
> >      i = s.index('bar')
> >      ...
> >   except ValueError from s.index as exc:
> >      <handle s.index ValueError>
> 
> 
> I can't imagine that this would even be *possible*, but even if it
> is, I would say it certainly isn't *desirable*.
> 
> (1) You're repeating code you expect to fail: you write s.index
> twice, even though it only gets called once.
> 
> (2) The semantics are messy and unclear. Suppose you have this:
> 
> try:
>     ...
>     i = s.index(a)
>     j = s.index(b) + s.index(c)
>     t = s
>     k = t.index(d)
>     method = s.index
>     l = method(e)
>     ...
> except ValueError from s.index:
>     ...
> 
> Which potential s.index exceptions will get caught? All of them? Some
> of them? Only i and j? What if you want to catch only some but not
> others?
[snip]

Maybe labeling interesting lines of code could be more suitable? E.g.:

    try:
        ...
        'risky one'
        i = s.index('bar')
        ...
    except ValueError from 'risky one' as exc:
        <handle ValueError raised at the line preceded by lone
         'risky one' string literal>

Cheers.
*j