"Steve Holden" <[EMAIL PROTECTED]> wrote: > George Sakkis wrote: > > Itertools is your friend in this case: > > > >>>>from itertools import takewhile > >>>>list(takewhile(p, xrange(10000000))) > > > > [0, 1] > > Maybe, but the code also implies an esoteric knowledge that the trught > value of the predicate is monotonically decreasing (in a Boolean sense). > This would not be true if (e.g.) p = lambda x: x % 2 == 0. So while > itertools.takewhile can save you unnecessary computations, such savings > rely on provable conditions of the predicate which are frequently false.
Right, it wasn't intended as a general solution for any p. For p = lambda x: x % 2 == 0, you do have to iterate till the iterator is consumed anyway, so a list comprehension is not less efficient (unless you replaced it with xrange(0,10000000,2), which again implies an esoteric knowledge of p; as usually, there's no free meal). George -- http://mail.python.org/mailman/listinfo/python-list
