550 lines
13 KiB
Python
550 lines
13 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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import itertools
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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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]
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### ONE-TRICK PONIES ###
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class Hashable:
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__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:
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__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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Iterable.register(str)
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class Iterator(Iterable):
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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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class Sized:
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__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:
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__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:
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__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(Sized, Iterable, Container):
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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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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 __gt__(self, other):
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if not isinstance(other, Set):
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return NotImplemented
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return other < self
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def __ge__(self, other):
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if not isinstance(other, Set):
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return NotImplemented
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return other <= self
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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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def __ne__(self, other):
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return not (self == 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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does not accept an iterable for an input.
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'''
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return cls(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.maxint
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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):
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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):
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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):
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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):
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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(Sized, Iterable, Container):
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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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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(Sized):
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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(type({}.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(type({}.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(type({}.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(Sized, Iterable, Container):
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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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def __iter__(self):
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i = 0
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try:
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while True:
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v = self[i]
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yield v
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i += 1
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except IndexError:
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return
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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(basestring)
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Sequence.register(buffer)
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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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