_itertools.py (607B)
- from itertools import filterfalse
- 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 filterfalse(seen.__contains__, iterable):
- seen_add(element)
- yield element
- else:
- for element in iterable:
- k = key(element)
- if k not in seen:
- seen_add(k)
- yield element