diff options
Diffstat (limited to 'Doc/library')
| -rw-r--r-- | Doc/library/itertools.rst | 29 |
1 files changed, 28 insertions, 1 deletions
diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst index fd77f99..254e055 100644 --- a/Doc/library/itertools.rst +++ b/Doc/library/itertools.rst @@ -837,6 +837,34 @@ which incur interpreter overhead. t1, t2 = tee(iterable) return filterfalse(pred, t1), filter(pred, t2) + def before_and_after(predicate, it): + """ Variant of takewhile() that allows complete + access to the remainder of the iterator. + + >>> all_upper, remainder = before_and_after(str.isupper, 'ABCdEfGhI') + >>> str.join('', all_upper) + 'ABC' + >>> str.join('', remainder) + 'dEfGhI' + + Note that the first iterator must be fully + consumed before the second iterator can + generate valid results. + """ + it = iter(it) + transition = [] + def true_iterator(): + for elem in it: + if predicate(elem): + yield elem + else: + transition.append(elem) + return + def remainder_iterator(): + yield from transition + yield from it + return true_iterator(), remainder_iterator() + def powerset(iterable): "powerset([1,2,3]) --> () (1,) (2,) (3,) (1,2) (1,3) (2,3) (1,2,3)" s = list(iterable) @@ -948,4 +976,3 @@ which incur interpreter overhead. c, n = c*(n-r)//n, n-1 result.append(pool[-1-n]) return tuple(result) - |