https://github.com/python/cpython/commit/18006309eac07e5f42232fd4ba016640aea... commit: 18006309eac07e5f42232fd4ba016640aeac5b1a branch: 3.11 author: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> committer: rhettinger <rhettinger@users.noreply.github.com> date: 2022-12-30T22:23:39-06:00 summary: [3.11] Improve comments in itertools uniquification recipes (GH-100631) (GH-100632) files: M Doc/library/itertools.rst diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst index 93bc1f792f54..fbbc96c60aba 100644 --- a/Doc/library/itertools.rst +++ b/Doc/library/itertools.rst @@ -989,15 +989,14 @@ which incur interpreter overhead. def unique_everseen(iterable, key=None): "List unique elements, preserving order. Remember all elements ever seen." # unique_everseen('AAAABBBCCDAABBB') --> A B C D - # unique_everseen('ABBCcAD', str.lower) --> A B C D + # unique_everseen('ABBcCAD', str.lower) --> A B c D seen = set() if key is None: for element in filterfalse(seen.__contains__, iterable): seen.add(element) yield element - # Note: The steps shown above are intended to demonstrate - # filterfalse(). For order preserving deduplication, - # a better solution is: + # For order preserving deduplication, + # a faster but non-lazy solution is: # yield from dict.fromkeys(iterable) else: for element in iterable: @@ -1005,11 +1004,15 @@ which incur interpreter overhead. if k not in seen: seen.add(k) yield element + # For use cases that allow the last matching element to be returned, + # a faster but non-lazy solution is: + # t1, t2 = tee(iterable) + # yield from dict(zip(map(key, t1), t2)).values() def unique_justseen(iterable, key=None): "List unique elements, preserving order. Remember only the element just seen." # unique_justseen('AAAABBBCCDAABBB') --> A B C D A B - # unique_justseen('ABBCcAD', str.lower) --> A B C A D + # unique_justseen('ABBcCAD', str.lower) --> A B c A D return map(next, map(operator.itemgetter(1), groupby(iterable, key))) def iter_except(func, exception, first=None): @@ -1365,15 +1368,17 @@ which incur interpreter overhead. >>> list(unique_everseen('AAAABBBCCDAABBB')) ['A', 'B', 'C', 'D'] - >>> list(unique_everseen('ABBCcAD', str.lower)) ['A', 'B', 'C', 'D'] + >>> list(unique_everseen('ABBcCAD', str.lower)) + ['A', 'B', 'c', 'D'] >>> list(unique_justseen('AAAABBBCCDAABBB')) ['A', 'B', 'C', 'D', 'A', 'B'] - >>> list(unique_justseen('ABBCcAD', str.lower)) ['A', 'B', 'C', 'A', 'D'] + >>> list(unique_justseen('ABBcCAD', str.lower)) + ['A', 'B', 'c', 'A', 'D'] >>> d = dict(a=1, b=2, c=3) >>> it = iter_except(d.popitem, KeyError)