Exception style

[Ben Finney]

"Fredrik Lundh" <fredrik at pythonware.com> writes:

> Cameron Laird wrote:
> > how do I know that the NameError means VARIABLE didn't resolve,
> > rather than that it did, but that evaluation of
> > commands.VARIABLE() itself didn't throw a NameError?  My usual
> > answer: umm, unless I go to efforts to prevent it, I *don't* know
> > that didn't happen.
> 
> two notes:
> 
> 1) getattr() raises an AttributeError if the attribute doesn't
> exist, not a NameError.
> 
> 2) as you point out, doing too much inside a single try/except often
> results in hard- to-find errors and confusing error messages.  the
> try-except-else pattern comes in handy in cases like this:
> 
>     try:
>         f = getattr(commands, name)
>     except AttributeError:
>         print "command", name, "not known"
>     else:
>         f()

Gah. As is often the case, Frederick has avoided my mistakes and said
what I wanted to say, better.

-- 
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Ben Finney