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