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Diffstat (limited to 'Doc/library/itertools.rst')
| -rw-r--r-- | Doc/library/itertools.rst | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst index ec0f533..2b27647 100644 --- a/Doc/library/itertools.rst +++ b/Doc/library/itertools.rst @@ -606,3 +606,27 @@ which incur interpreter overhead. return indices[i:] = [indices[i] + 1] * (r - i) yield tuple(pool[i] for i in indices) + + 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 + seen = set() + seen_add = seen.add + if key is None: + for element in iterable: + if element not in seen: + seen_add(element) + yield element + else: + for element in iterable: + k = key(element) + if k not in seen: + seen_add(k) + yield element + + 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 + return map(next, map(itemgetter(1), groupby(iterable, key))) |