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+# Copyright 2007 Google, Inc. All Rights Reserved.
+# Licensed to PSF under a Contributor Agreement.
+
+"""Abstract Base Classes (ABCs) for collections, according to PEP 3119.
+
+DON'T USE THIS MODULE DIRECTLY! The classes here should be imported
+via collections; they are defined here only to alleviate ceratin
+bootstrapping issues. Unit tests are in test_collections.
+"""
+
+from abc import ABCMeta, abstractmethod
+
+__all__ = ["Hashable", "Iterable", "Iterator",
+ "Sized", "Container", "Callable",
+ "Set", "MutableSet",
+ "Mapping", "MutableMapping",
+ "MappingView", "KeysView", "ItemsView", "ValuesView",
+ "Sequence", "MutableSequence",
+ ]
+
+### ONE-TRICK PONIES ###
+
+class Hashable(metaclass=ABCMeta):
+
+ @abstractmethod
+ def __hash__(self):
+ return 0
+
+ @classmethod
+ def __subclasshook__(cls, C):
+ if cls is Hashable:
+ for B in C.__mro__:
+ if "__hash__" in B.__dict__:
+ if B.__dict__["__hash__"]:
+ return True
+ break
+ return NotImplemented
+
+
+class Iterable(metaclass=ABCMeta):
+
+ @abstractmethod
+ def __iter__(self):
+ while False:
+ yield None
+
+ @classmethod
+ def __subclasshook__(cls, C):
+ if cls is Iterable:
+ if any("__iter__" in B.__dict__ for B in C.__mro__):
+ return True
+ return NotImplemented
+
+Iterable.register(bytes)
+
+
+class Iterator(metaclass=ABCMeta):
+
+ @abstractmethod
+ def __next__(self):
+ raise StopIteration
+
+ def __iter__(self):
+ return self
+
+ @classmethod
+ def __subclasshook__(cls, C):
+ if cls is Iterator:
+ if any("__next__" in B.__dict__ for B in C.__mro__):
+ return True
+ return NotImplemented
+
+
+class Sized(metaclass=ABCMeta):
+
+ @abstractmethod
+ def __len__(self):
+ return 0
+
+ @classmethod
+ def __subclasshook__(cls, C):
+ if cls is Sized:
+ if any("__len__" in B.__dict__ for B in C.__mro__):
+ return True
+ return NotImplemented
+
+
+class Container(metaclass=ABCMeta):
+
+ @abstractmethod
+ def __contains__(self, x):
+ return False
+
+ @classmethod
+ def __subclasshook__(cls, C):
+ if cls is Container:
+ if any("__contains__" in B.__dict__ for B in C.__mro__):
+ return True
+ return NotImplemented
+
+
+class Callable(metaclass=ABCMeta):
+
+ @abstractmethod
+ def __contains__(self, x):
+ return False
+
+ @classmethod
+ def __subclasshook__(cls, C):
+ if cls is Callable:
+ if any("__call__" in B.__dict__ for B in C.__mro__):
+ return True
+ return NotImplemented
+
+
+### SETS ###
+
+
+class Set(metaclass=ABCMeta):
+
+ """A set is a finite, iterable container.
+
+ This class provides concrete generic implementations of all
+ methods except for __contains__, __iter__ and __len__.
+
+ To override the comparisons (presumably for speed, as the
+ semantics are fixed), all you have to do is redefine __le__ and
+ then the other operations will automatically follow suit.
+ """
+
+ @abstractmethod
+ def __contains__(self, value):
+ return False
+
+ @abstractmethod
+ def __iter__(self):
+ while False:
+ yield None
+
+ @abstractmethod
+ def __len__(self):
+ return 0
+
+ def __le__(self, other):
+ if not isinstance(other, Set):
+ return NotImplemented
+ if len(self) > len(other):
+ return False
+ for elem in self:
+ if elem not in other:
+ return False
+ return True
+
+ def __lt__(self, other):
+ if not isinstance(other, Set):
+ return NotImplemented
+ return len(self) < len(other) and self.__le__(other)
+
+ def __eq__(self, other):
+ if not isinstance(other, Set):
+ return NotImplemented
+ return len(self) == len(other) and self.__le__(other)
+
+ @classmethod
+ def _from_iterable(cls, it):
+ return frozenset(it)
+
+ def __and__(self, other):
+ if not isinstance(other, Iterable):
+ return NotImplemented
+ return self._from_iterable(value for value in other if value in self)
+
+ def __or__(self, other):
+ if not isinstance(other, Iterable):
+ return NotImplemented
+ return self._from_iterable(itertools.chain(self, other))
+
+ def __sub__(self, other):
+ if not isinstance(other, Set):
+ if not isinstance(other, Iterable):
+ return NotImplemented
+ other = self._from_iterable(other)
+ return self._from_iterable(value for value in self
+ if value not in other)
+
+ def __xor__(self, other):
+ if not isinstance(other, Set):
+ if not isinstance(other, Iterable):
+ return NotImplemented
+ other = self._from_iterable(other)
+ return (self - other) | (other - self)
+
+ def _hash(self):
+ """Compute the hash value of a set.
+
+ Note that we don't define __hash__: not all sets are hashable.
+ But if you define a hashable set type, its __hash__ should
+ call this function.
+
+ This must be compatible __eq__.
+
+ All sets ought to compare equal if they contain the same
+ elements, regardless of how they are implemented, and
+ regardless of the order of the elements; so there's not much
+ freedom for __eq__ or __hash__. We match the algorithm used
+ by the built-in frozenset type.
+ """
+ MAX = sys.maxint
+ MASK = 2 * MAX + 1
+ n = len(self)
+ h = 1927868237 * (n + 1)
+ h &= MASK
+ for x in self:
+ hx = hash(x)
+ h ^= (hx ^ (hx << 16) ^ 89869747) * 3644798167
+ h &= MASK
+ h = h * 69069 + 907133923
+ h &= MASK
+ if h > MAX:
+ h -= MASK + 1
+ if h == -1:
+ h = 590923713
+ return h
+
+Set.register(frozenset)
+
+
+class MutableSet(Set):
+
+ @abstractmethod
+ def add(self, value):
+ """Return True if it was added, False if already there."""
+ raise NotImplementedError
+
+ @abstractmethod
+ def discard(self, value):
+ """Return True if it was deleted, False if not there."""
+ raise NotImplementedError
+
+ def pop(self):
+ """Return the popped value. Raise KeyError if empty."""
+ it = iter(self)
+ try:
+ value = it.__next__()
+ except StopIteration:
+ raise KeyError
+ self.discard(value)
+ return value
+
+ def toggle(self, value):
+ """Return True if it was added, False if deleted."""
+ # XXX This implementation is not thread-safe
+ if value in self:
+ self.discard(value)
+ return False
+ else:
+ self.add(value)
+ return True
+
+ def clear(self):
+ """This is slow (creates N new iterators!) but effective."""
+ try:
+ while True:
+ self.pop()
+ except KeyError:
+ pass
+
+ def __ior__(self, it: Iterable):
+ for value in it:
+ self.add(value)
+ return self
+
+ def __iand__(self, c: Container):
+ for value in self:
+ if value not in c:
+ self.discard(value)
+ return self
+
+ def __ixor__(self, it: Iterable):
+ # This calls toggle(), so if that is overridded, we call the override
+ for value in it:
+ self.toggle(it)
+ return self
+
+ def __isub__(self, it: Iterable):
+ for value in it:
+ self.discard(value)
+ return self
+
+MutableSet.register(set)
+
+
+### MAPPINGS ###
+
+
+class Mapping(metaclass=ABCMeta):
+
+ @abstractmethod
+ def __getitem__(self, key):
+ raise KeyError
+
+ def get(self, key, default=None):
+ try:
+ return self[key]
+ except KeyError:
+ return default
+
+ def __contains__(self, key):
+ try:
+ self[key]
+ except KeyError:
+ return False
+ else:
+ return True
+
+ @abstractmethod
+ def __len__(self):
+ return 0
+
+ @abstractmethod
+ def __iter__(self):
+ while False:
+ yield None
+
+ def keys(self):
+ return KeysView(self)
+
+ def items(self):
+ return ItemsView(self)
+
+ def values(self):
+ return ValuesView(self)
+
+
+class MappingView(metaclass=ABCMeta):
+
+ def __init__(self, mapping):
+ self._mapping = mapping
+
+ def __len__(self):
+ return len(self._mapping)
+
+
+class KeysView(MappingView, Set):
+
+ def __contains__(self, key):
+ return key in self._mapping
+
+ def __iter__(self):
+ for key in self._mapping:
+ yield key
+
+KeysView.register(type({}.keys()))
+
+
+class ItemsView(MappingView, Set):
+
+ def __contains__(self, item):
+ key, value = item
+ try:
+ v = self._mapping[key]
+ except KeyError:
+ return False
+ else:
+ return v == value
+
+ def __iter__(self):
+ for key in self._mapping:
+ yield (key, self._mapping[key])
+
+ItemsView.register(type({}.items()))
+
+
+class ValuesView(MappingView):
+
+ def __contains__(self, value):
+ for key in self._mapping:
+ if value == self._mapping[key]:
+ return True
+ return False
+
+ def __iter__(self):
+ for key in self._mapping:
+ yield self._mapping[key]
+
+ValuesView.register(type({}.values()))
+
+
+class MutableMapping(Mapping):
+
+ @abstractmethod
+ def __setitem__(self, key, value):
+ raise KeyError
+
+ @abstractmethod
+ def __delitem__(self, key):
+ raise KeyError
+
+ __marker = object()
+
+ def pop(self, key, default=__marker):
+ try:
+ value = self[key]
+ except KeyError:
+ if default is self.__marker:
+ raise
+ return default
+ else:
+ del self[key]
+ return value
+
+ def popitem(self):
+ try:
+ key = next(iter(self))
+ except StopIteration:
+ raise KeyError
+ value = self[key]
+ del self[key]
+ return key, value
+
+ def clear(self):
+ try:
+ while True:
+ self.popitem()
+ except KeyError:
+ pass
+
+ def update(self, other=(), **kwds):
+ if isinstance(other, Mapping):
+ for key in other:
+ self[key] = other[key]
+ elif hasattr(other, "keys"):
+ for key in other.keys():
+ self[key] = other[key]
+ else:
+ for key, value in other:
+ self[key] = value
+ for key, value in kwds.items():
+ self[key] = value
+
+MutableMapping.register(dict)
+
+
+### SEQUENCES ###
+
+
+class Sequence(metaclass=ABCMeta):
+
+ """All the operations on a read-only sequence.
+
+ Concrete subclasses must override __new__ or __init__,
+ __getitem__, and __len__.
+ """
+
+ @abstractmethod
+ def __getitem__(self, index):
+ raise IndexError
+
+ @abstractmethod
+ def __len__(self):
+ return 0
+
+ def __iter__(self):
+ i = 0
+ while True:
+ try:
+ v = self[i]
+ except IndexError:
+ break
+ yield v
+ i += 1
+
+ def __contains__(self, value):
+ for v in self:
+ if v == value:
+ return True
+ return False
+
+ def __reversed__(self):
+ for i in reversed(range(len(self))):
+ yield self[i]
+
+ def index(self, value):
+ for i, v in enumerate(self):
+ if v == value:
+ return i
+ raise ValueError
+
+ def count(self, value):
+ return sum(1 for v in self if v == value)
+
+Sequence.register(tuple)
+Sequence.register(basestring)
+Sequence.register(buffer)
+
+
+class MutableSequence(Sequence):
+
+ @abstractmethod
+ def __setitem__(self, index, value):
+ raise IndexError
+
+ @abstractmethod
+ def __delitem__(self, index):
+ raise IndexError
+
+ @abstractmethod
+ def insert(self, index, value):
+ raise IndexError
+
+ def append(self, value):
+ self.insert(len(self), value)
+
+ def reverse(self):
+ n = len(self)
+ for i in range(n//2):
+ self[i], self[n-i-1] = self[n-i-1], self[i]
+
+ def extend(self, values):
+ for v in values:
+ self.append(v)
+
+ def pop(self, index=-1):
+ v = self[index]
+ del self[index]
+ return v
+
+ def remove(self, value):
+ del self[self.index(value)]
+
+ def __iadd__(self, values):
+ self.extend(values)
+
+MutableSequence.register(list)
+MutableSequence.register(bytes)
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