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Re: Idioms combining 'next(items)' and 'for item in items:'

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  Re: Idioms combining 'next(items)' and 'for item in items:' Ian Kelly <ian.g.kelly@gmail.com> - 2011-09-12 10:55 -0600

#13189 — Re: Idioms combining 'next(items)' and 'for item in items:'

On Sun, Sep 11, 2011 at 6:45 PM, Terry Reedy <tjreedy@udel.edu> wrote:
> whereas, you are right, it breaks it noisily in the body. So Ian's claim
> that StopIteration must be caught to avoid silent termination is not true.
> Thanks for pointing out what I saw but did not cognize the full implication
> of before. A better exception and an error message with an explaination
> might still be a good idea, though.

But you can't write the function under the assumption that it will
only be called from the function body.  The following is a slight
reorganization of your example that does exhibit the problem:

for title in map(fix_title, ['amazinG', 'a helL of a fiGHT', '', 'igNordEd']):
    print(title)

Output:
amazing
a Hell of a Fight

Note that at first glance, my example would appear to be functionally
equivalent to yours -- I've merely pulled the fix_title call out of
the loop body and into the iterator.  But actually they produce
different results because fix_title misbehaves by not catching the
StopIteration.

Cheers,
Ian

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