Thanks for the comment and discussion guys.
Bottom line, I'm going to have to remove this pattern from my code:
foo = (foo for foo in foos if foo.bar).next()
I used to have that a lot in cases where not finding at least one
valid foo is an actual fatal error. But using StopIteration to signal
a fatal condition becomes a bug when interacting with list() as shown
in the original post.
It would be nice if there was a builtin for "get the first element in
a genexp, or raise an exception (which isn't StopIteration)", sort of
like:
from itertools import islice
def first_or_raise(genexp):
L = list(islice(genexp, 1))
if not L:
raise RuntimeError('no elements found')
return L[0]
I also think Jean-Paul's had a good point about how the problems in
the list/genexp interaction could be addressed.
Thank you,
-- Tom
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