Tom Machinski wrote:
> 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]
Somewhat related in 2.6 there's the next() built-in which accepts a default
value. You can provide a sentinel and test for that instead of using
try...except:
>>> from random import randrange
>>> from functools import partial
>>> def g():
... return iter(partial(randrange, 3), 2)
...
>>> next(g(), "empty")
1
>>> next(g(), "empty")
1
>>> next(g(), "empty")
'empty'
>>> next(g(), "empty")
'empty'
>>> next(g(), "empty")
'empty'
>>> next(g(), "empty")
0
Peter
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