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8284c4a7fb
In its previous form, it always returned instance of frozenset which makes this ABC nearly useless as a mixin. In its new form, it needs to be able to assume that the constructor will take a frozenset input. This will usually be true. If it is not, then only one method (this one) will need to be overriden by the subclass to let it know about the unique constructor signature. Will add info on this to the docs.
611 lines
15 KiB
Python
611 lines
15 KiB
Python
# Copyright 2007 Google, Inc. All Rights Reserved.
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# Licensed to PSF under a Contributor Agreement.
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"""Abstract Base Classes (ABCs) for collections, according to PEP 3119.
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DON'T USE THIS MODULE DIRECTLY! The classes here should be imported
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via collections; they are defined here only to alleviate certain
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bootstrapping issues. Unit tests are in test_collections.
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"""
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from abc import ABCMeta, abstractmethod
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__all__ = ["Hashable", "Iterable", "Iterator",
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"Sized", "Container", "Callable",
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"Set", "MutableSet",
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"Mapping", "MutableMapping",
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"MappingView", "KeysView", "ItemsView", "ValuesView",
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"Sequence", "MutableSequence",
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"ByteString",
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"bytearray_iterator", "bytes_iterator", "dict_itemiterator",
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"dict_items", "dict_keyiterator", "dict_keys", "dict_proxy",
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"dict_valueiterator", "dict_values", "list_iterator",
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"list_reverseiterator", "range_iterator", "set_iterator",
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"str_iterator", "tuple_iterator", "zip_iterator",
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]
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### collection related types which are not exposed through builtin ###
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## iterators ##
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bytes_iterator = type(iter(b''))
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bytearray_iterator = type(iter(bytearray()))
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#callable_iterator = ???
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dict_keyiterator = type(iter({}.keys()))
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dict_valueiterator = type(iter({}.values()))
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dict_itemiterator = type(iter({}.items()))
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list_iterator = type(iter([]))
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list_reverseiterator = type(iter(reversed([])))
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range_iterator = type(iter(range(0)))
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set_iterator = type(iter(set()))
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str_iterator = type(iter(""))
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tuple_iterator = type(iter(()))
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zip_iterator = type(iter(zip()))
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## views ##
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dict_keys = type({}.keys())
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dict_values = type({}.values())
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dict_items = type({}.items())
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## misc ##
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dict_proxy = type(type.__dict__)
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### ONE-TRICK PONIES ###
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class Hashable(metaclass=ABCMeta):
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@abstractmethod
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def __hash__(self):
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return 0
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@classmethod
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def __subclasshook__(cls, C):
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if cls is Hashable:
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for B in C.__mro__:
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if "__hash__" in B.__dict__:
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if B.__dict__["__hash__"]:
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return True
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break
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return NotImplemented
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class Iterable(metaclass=ABCMeta):
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@abstractmethod
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def __iter__(self):
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while False:
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yield None
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@classmethod
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def __subclasshook__(cls, C):
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if cls is Iterable:
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if any("__iter__" in B.__dict__ for B in C.__mro__):
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return True
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return NotImplemented
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class Iterator(metaclass=ABCMeta):
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@abstractmethod
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def __next__(self):
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raise StopIteration
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def __iter__(self):
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return self
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@classmethod
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def __subclasshook__(cls, C):
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if cls is Iterator:
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if any("__next__" in B.__dict__ for B in C.__mro__):
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return True
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return NotImplemented
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Iterator.register(bytes_iterator)
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Iterator.register(bytearray_iterator)
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#Iterator.register(callable_iterator)
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Iterator.register(dict_keyiterator)
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Iterator.register(dict_valueiterator)
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Iterator.register(dict_itemiterator)
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Iterator.register(list_iterator)
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Iterator.register(list_reverseiterator)
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Iterator.register(range_iterator)
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Iterator.register(set_iterator)
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Iterator.register(str_iterator)
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Iterator.register(tuple_iterator)
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Iterator.register(zip_iterator)
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class Sized(metaclass=ABCMeta):
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@abstractmethod
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def __len__(self):
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return 0
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@classmethod
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def __subclasshook__(cls, C):
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if cls is Sized:
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if any("__len__" in B.__dict__ for B in C.__mro__):
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return True
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return NotImplemented
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class Container(metaclass=ABCMeta):
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@abstractmethod
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def __contains__(self, x):
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return False
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@classmethod
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def __subclasshook__(cls, C):
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if cls is Container:
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if any("__contains__" in B.__dict__ for B in C.__mro__):
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return True
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return NotImplemented
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class Callable(metaclass=ABCMeta):
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@abstractmethod
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def __contains__(self, x):
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return False
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@classmethod
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def __subclasshook__(cls, C):
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if cls is Callable:
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if any("__call__" in B.__dict__ for B in C.__mro__):
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return True
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return NotImplemented
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### SETS ###
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class Set(metaclass=ABCMeta):
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"""A set is a finite, iterable container.
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This class provides concrete generic implementations of all
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methods except for __contains__, __iter__ and __len__.
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To override the comparisons (presumably for speed, as the
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semantics are fixed), all you have to do is redefine __le__ and
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then the other operations will automatically follow suit.
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"""
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@abstractmethod
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def __contains__(self, value):
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return False
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@abstractmethod
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def __iter__(self):
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while False:
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yield None
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@abstractmethod
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def __len__(self):
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return 0
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def __le__(self, other):
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if not isinstance(other, Set):
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return NotImplemented
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if len(self) > len(other):
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return False
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for elem in self:
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if elem not in other:
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return False
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return True
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def __lt__(self, other):
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if not isinstance(other, Set):
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return NotImplemented
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return len(self) < len(other) and self.__le__(other)
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def __eq__(self, other):
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if not isinstance(other, Set):
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return NotImplemented
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return len(self) == len(other) and self.__le__(other)
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@classmethod
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def _from_iterable(cls, it):
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'''Construct an instance of the class from any iterable input.
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Must override this method if the class constructor signature
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will not accept a frozenset for an input.
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'''
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return cls(frozenset(it))
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def __and__(self, other):
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if not isinstance(other, Iterable):
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return NotImplemented
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return self._from_iterable(value for value in other if value in self)
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def isdisjoint(self, other):
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for value in other:
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if value in self:
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return False
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return True
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def __or__(self, other):
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if not isinstance(other, Iterable):
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return NotImplemented
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return self._from_iterable(itertools.chain(self, other))
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def __sub__(self, other):
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if not isinstance(other, Set):
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if not isinstance(other, Iterable):
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return NotImplemented
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other = self._from_iterable(other)
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return self._from_iterable(value for value in self
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if value not in other)
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def __xor__(self, other):
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if not isinstance(other, Set):
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if not isinstance(other, Iterable):
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return NotImplemented
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other = self._from_iterable(other)
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return (self - other) | (other - self)
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def _hash(self):
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"""Compute the hash value of a set.
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Note that we don't define __hash__: not all sets are hashable.
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But if you define a hashable set type, its __hash__ should
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call this function.
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This must be compatible __eq__.
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All sets ought to compare equal if they contain the same
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elements, regardless of how they are implemented, and
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regardless of the order of the elements; so there's not much
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freedom for __eq__ or __hash__. We match the algorithm used
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by the built-in frozenset type.
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"""
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MAX = sys.maxsize
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MASK = 2 * MAX + 1
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n = len(self)
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h = 1927868237 * (n + 1)
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h &= MASK
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for x in self:
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hx = hash(x)
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h ^= (hx ^ (hx << 16) ^ 89869747) * 3644798167
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h &= MASK
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h = h * 69069 + 907133923
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h &= MASK
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if h > MAX:
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h -= MASK + 1
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if h == -1:
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h = 590923713
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return h
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Set.register(frozenset)
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class MutableSet(Set):
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@abstractmethod
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def add(self, value):
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"""Return True if it was added, False if already there."""
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raise NotImplementedError
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@abstractmethod
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def discard(self, value):
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"""Return True if it was deleted, False if not there."""
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raise NotImplementedError
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def remove(self, value):
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"""Remove an element. If not a member, raise a KeyError."""
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if value not in self:
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raise KeyError(value)
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self.discard(value)
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def pop(self):
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"""Return the popped value. Raise KeyError if empty."""
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it = iter(self)
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try:
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value = it.__next__()
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except StopIteration:
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raise KeyError
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self.discard(value)
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return value
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def clear(self):
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"""This is slow (creates N new iterators!) but effective."""
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try:
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while True:
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self.pop()
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except KeyError:
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pass
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def __ior__(self, it: Iterable):
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for value in it:
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self.add(value)
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return self
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def __iand__(self, c: Container):
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for value in self:
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if value not in c:
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self.discard(value)
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return self
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def __ixor__(self, it: Iterable):
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if not isinstance(it, Set):
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it = self._from_iterable(it)
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for value in it:
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if value in self:
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self.discard(value)
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else:
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self.add(value)
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return self
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def __isub__(self, it: Iterable):
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for value in it:
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self.discard(value)
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return self
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MutableSet.register(set)
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### MAPPINGS ###
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class Mapping(metaclass=ABCMeta):
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@abstractmethod
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def __getitem__(self, key):
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raise KeyError
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def get(self, key, default=None):
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try:
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return self[key]
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except KeyError:
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return default
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def __contains__(self, key):
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try:
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self[key]
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except KeyError:
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return False
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else:
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return True
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@abstractmethod
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def __len__(self):
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return 0
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@abstractmethod
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def __iter__(self):
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while False:
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yield None
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def keys(self):
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return KeysView(self)
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def items(self):
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return ItemsView(self)
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def values(self):
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return ValuesView(self)
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def __eq__(self, other):
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return isinstance(other, Mapping) and \
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dict(self.items()) == dict(other.items())
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def __ne__(self, other):
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return not (self == other)
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class MappingView(metaclass=ABCMeta):
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def __init__(self, mapping):
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self._mapping = mapping
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def __len__(self):
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return len(self._mapping)
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class KeysView(MappingView, Set):
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def __contains__(self, key):
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return key in self._mapping
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def __iter__(self):
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for key in self._mapping:
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yield key
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KeysView.register(dict_keys)
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class ItemsView(MappingView, Set):
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def __contains__(self, item):
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key, value = item
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try:
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v = self._mapping[key]
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except KeyError:
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return False
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else:
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return v == value
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def __iter__(self):
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for key in self._mapping:
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yield (key, self._mapping[key])
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ItemsView.register(dict_items)
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class ValuesView(MappingView):
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def __contains__(self, value):
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for key in self._mapping:
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if value == self._mapping[key]:
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return True
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return False
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def __iter__(self):
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for key in self._mapping:
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yield self._mapping[key]
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ValuesView.register(dict_values)
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class MutableMapping(Mapping):
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@abstractmethod
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def __setitem__(self, key, value):
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raise KeyError
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@abstractmethod
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def __delitem__(self, key):
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raise KeyError
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__marker = object()
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def pop(self, key, default=__marker):
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try:
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value = self[key]
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except KeyError:
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if default is self.__marker:
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raise
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return default
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else:
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del self[key]
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return value
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def popitem(self):
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try:
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key = next(iter(self))
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except StopIteration:
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raise KeyError
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value = self[key]
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del self[key]
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return key, value
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def clear(self):
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try:
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while True:
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self.popitem()
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except KeyError:
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pass
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def update(self, other=(), **kwds):
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if isinstance(other, Mapping):
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for key in other:
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self[key] = other[key]
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elif hasattr(other, "keys"):
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for key in other.keys():
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self[key] = other[key]
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else:
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for key, value in other:
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self[key] = value
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for key, value in kwds.items():
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self[key] = value
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def setdefault(self, key, default=None):
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try:
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return self[key]
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except KeyError:
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self[key] = default
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return default
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MutableMapping.register(dict)
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### SEQUENCES ###
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class Sequence(metaclass=ABCMeta):
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"""All the operations on a read-only sequence.
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Concrete subclasses must override __new__ or __init__,
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__getitem__, and __len__.
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"""
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@abstractmethod
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def __getitem__(self, index):
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raise IndexError
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@abstractmethod
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def __len__(self):
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return 0
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def __iter__(self):
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i = 0
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while True:
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try:
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v = self[i]
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except IndexError:
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break
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yield v
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i += 1
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def __contains__(self, value):
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for v in self:
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if v == value:
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return True
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return False
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def __reversed__(self):
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for i in reversed(range(len(self))):
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yield self[i]
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def index(self, value):
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for i, v in enumerate(self):
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if v == value:
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return i
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raise ValueError
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def count(self, value):
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return sum(1 for v in self if v == value)
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Sequence.register(tuple)
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Sequence.register(str)
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class ByteString(Sequence):
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"""This unifies bytes and bytearray.
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XXX Should add all their methods.
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"""
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ByteString.register(bytes)
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ByteString.register(bytearray)
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class MutableSequence(Sequence):
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@abstractmethod
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def __setitem__(self, index, value):
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raise IndexError
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@abstractmethod
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def __delitem__(self, index):
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raise IndexError
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@abstractmethod
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def insert(self, index, value):
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raise IndexError
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def append(self, value):
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self.insert(len(self), value)
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def reverse(self):
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n = len(self)
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for i in range(n//2):
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self[i], self[n-i-1] = self[n-i-1], self[i]
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def extend(self, values):
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for v in values:
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self.append(v)
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def pop(self, index=-1):
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v = self[index]
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del self[index]
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return v
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def remove(self, value):
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del self[self.index(value)]
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def __iadd__(self, values):
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self.extend(values)
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MutableSequence.register(list)
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MutableSequence.register(bytearray) # Multiply inheriting, see ByteString
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