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74 lines
2.0 KiB
Python
74 lines
2.0 KiB
Python
2 years ago
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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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# copied from more_itertools 8.8
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def always_iterable(obj, base_type=(str, bytes)):
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"""If *obj* is iterable, return an iterator over its items::
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>>> obj = (1, 2, 3)
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>>> list(always_iterable(obj))
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[1, 2, 3]
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If *obj* is not iterable, return a one-item iterable containing *obj*::
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>>> obj = 1
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>>> list(always_iterable(obj))
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[1]
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If *obj* is ``None``, return an empty iterable:
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>>> obj = None
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>>> list(always_iterable(None))
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[]
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By default, binary and text strings are not considered iterable::
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>>> obj = 'foo'
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>>> list(always_iterable(obj))
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['foo']
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If *base_type* is set, objects for which ``isinstance(obj, base_type)``
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returns ``True`` won't be considered iterable.
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>>> obj = {'a': 1}
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>>> list(always_iterable(obj)) # Iterate over the dict's keys
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['a']
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>>> list(always_iterable(obj, base_type=dict)) # Treat dicts as a unit
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[{'a': 1}]
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Set *base_type* to ``None`` to avoid any special handling and treat objects
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Python considers iterable as iterable:
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>>> obj = 'foo'
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>>> list(always_iterable(obj, base_type=None))
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['f', 'o', 'o']
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"""
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if obj is None:
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return iter(())
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if (base_type is not None) and isinstance(obj, base_type):
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return iter((obj,))
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try:
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return iter(obj)
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except TypeError:
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return iter((obj,))
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