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20 lines
607 B
Python
20 lines
607 B
Python
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from itertools import filterfalse
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def unique_everseen(iterable, key=None):
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"List unique elements, preserving order. Remember all elements ever seen."
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# unique_everseen('AAAABBBCCDAABBB') --> A B C D
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# unique_everseen('ABBCcAD', str.lower) --> A B C D
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seen = set()
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seen_add = seen.add
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if key is None:
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for element in filterfalse(seen.__contains__, iterable):
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seen_add(element)
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yield element
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else:
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for element in iterable:
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k = key(element)
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if k not in seen:
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seen_add(k)
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yield element
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