Issue #11085: Moved collections abstract base classes into a separate module
called collections.abc, following the pattern used by importlib.abc. For
backwards compatibility, the names continue to also be imported into the
collections module.
diff --git a/Lib/collections/abc.py b/Lib/collections/abc.py
new file mode 100644
index 0000000..6e908bd
--- /dev/null
+++ b/Lib/collections/abc.py
@@ -0,0 +1,621 @@
+# Copyright 2007 Google, Inc. All Rights Reserved.
+# Licensed to PSF under a Contributor Agreement.
+
+"""Abstract Base Classes (ABCs) for collections, according to PEP 3119.
+
+Unit tests are in test_collections.
+"""
+
+from abc import ABCMeta, abstractmethod
+import sys
+
+__all__ = ["Hashable", "Iterable", "Iterator",
+ "Sized", "Container", "Callable",
+ "Set", "MutableSet",
+ "Mapping", "MutableMapping",
+ "MappingView", "KeysView", "ItemsView", "ValuesView",
+ "Sequence", "MutableSequence",
+ "ByteString",
+ ]
+
+
+### collection related types which are not exposed through builtin ###
+## iterators ##
+bytes_iterator = type(iter(b''))
+bytearray_iterator = type(iter(bytearray()))
+#callable_iterator = ???
+dict_keyiterator = type(iter({}.keys()))
+dict_valueiterator = type(iter({}.values()))
+dict_itemiterator = type(iter({}.items()))
+list_iterator = type(iter([]))
+list_reverseiterator = type(iter(reversed([])))
+range_iterator = type(iter(range(0)))
+set_iterator = type(iter(set()))
+str_iterator = type(iter(""))
+tuple_iterator = type(iter(()))
+zip_iterator = type(iter(zip()))
+## views ##
+dict_keys = type({}.keys())
+dict_values = type({}.values())
+dict_items = type({}.items())
+## misc ##
+dict_proxy = type(type.__dict__)
+
+
+### 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
+
+
+class Iterator(Iterable):
+
+ @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__) and
+ any("__iter__" in B.__dict__ for B in C.__mro__)):
+ return True
+ return NotImplemented
+
+Iterator.register(bytes_iterator)
+Iterator.register(bytearray_iterator)
+#Iterator.register(callable_iterator)
+Iterator.register(dict_keyiterator)
+Iterator.register(dict_valueiterator)
+Iterator.register(dict_itemiterator)
+Iterator.register(list_iterator)
+Iterator.register(list_reverseiterator)
+Iterator.register(range_iterator)
+Iterator.register(set_iterator)
+Iterator.register(str_iterator)
+Iterator.register(tuple_iterator)
+Iterator.register(zip_iterator)
+
+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 __call__(self, *args, **kwds):
+ 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(Sized, Iterable, Container):
+
+ """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.
+ """
+
+ 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 __gt__(self, other):
+ if not isinstance(other, Set):
+ return NotImplemented
+ return other < self
+
+ def __ge__(self, other):
+ if not isinstance(other, Set):
+ return NotImplemented
+ return other <= self
+
+ def __eq__(self, other):
+ if not isinstance(other, Set):
+ return NotImplemented
+ return len(self) == len(other) and self.__le__(other)
+
+ def __ne__(self, other):
+ return not (self == other)
+
+ @classmethod
+ def _from_iterable(cls, it):
+ '''Construct an instance of the class from any iterable input.
+
+ Must override this method if the class constructor signature
+ does not accept an iterable for an input.
+ '''
+ return cls(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 isdisjoint(self, other):
+ for value in other:
+ if value in self:
+ return False
+ return True
+
+ def __or__(self, other):
+ if not isinstance(other, Iterable):
+ return NotImplemented
+ chain = (e for s in (self, other) for e in s)
+ return self._from_iterable(chain)
+
+ 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.maxsize
+ 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):
+ """Add an element."""
+ raise NotImplementedError
+
+ @abstractmethod
+ def discard(self, value):
+ """Remove an element. Do not raise an exception if absent."""
+ raise NotImplementedError
+
+ def remove(self, value):
+ """Remove an element. If not a member, raise a KeyError."""
+ if value not in self:
+ raise KeyError(value)
+ self.discard(value)
+
+ def pop(self):
+ """Return the popped value. Raise KeyError if empty."""
+ it = iter(self)
+ try:
+ value = next(it)
+ except StopIteration:
+ raise KeyError
+ self.discard(value)
+ return value
+
+ def clear(self):
+ """This is slow (creates N new iterators!) but effective."""
+ try:
+ while True:
+ self.pop()
+ except KeyError:
+ pass
+
+ def __ior__(self, it):
+ for value in it:
+ self.add(value)
+ return self
+
+ def __iand__(self, it):
+ for value in (self - it):
+ self.discard(value)
+ return self
+
+ def __ixor__(self, it):
+ if it is self:
+ self.clear()
+ else:
+ if not isinstance(it, Set):
+ it = self._from_iterable(it)
+ for value in it:
+ if value in self:
+ self.discard(value)
+ else:
+ self.add(value)
+ return self
+
+ def __isub__(self, it):
+ if it is self:
+ self.clear()
+ else:
+ for value in it:
+ self.discard(value)
+ return self
+
+MutableSet.register(set)
+
+
+### MAPPINGS ###
+
+
+class Mapping(Sized, Iterable, Container):
+
+ @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
+
+ def keys(self):
+ return KeysView(self)
+
+ def items(self):
+ return ItemsView(self)
+
+ def values(self):
+ return ValuesView(self)
+
+ def __eq__(self, other):
+ if not isinstance(other, Mapping):
+ return NotImplemented
+ return dict(self.items()) == dict(other.items())
+
+ def __ne__(self, other):
+ return not (self == other)
+
+
+class MappingView(Sized):
+
+ def __init__(self, mapping):
+ self._mapping = mapping
+
+ def __len__(self):
+ return len(self._mapping)
+
+ def __repr__(self):
+ return '{0.__class__.__name__}({0._mapping!r})'.format(self)
+
+
+class KeysView(MappingView, Set):
+
+ @classmethod
+ def _from_iterable(self, it):
+ return set(it)
+
+ def __contains__(self, key):
+ return key in self._mapping
+
+ def __iter__(self):
+ for key in self._mapping:
+ yield key
+
+KeysView.register(dict_keys)
+
+
+class ItemsView(MappingView, Set):
+
+ @classmethod
+ def _from_iterable(self, it):
+ return set(it)
+
+ 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(dict_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(dict_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(*args, **kwds):
+ if len(args) > 2:
+ raise TypeError("update() takes at most 2 positional "
+ "arguments ({} given)".format(len(args)))
+ elif not args:
+ raise TypeError("update() takes at least 1 argument (0 given)")
+ self = args[0]
+ other = args[1] if len(args) >= 2 else ()
+
+ 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
+
+ def setdefault(self, key, default=None):
+ try:
+ return self[key]
+ except KeyError:
+ self[key] = default
+ return default
+
+MutableMapping.register(dict)
+
+
+### SEQUENCES ###
+
+
+class Sequence(Sized, Iterable, Container):
+
+ """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
+
+ def __iter__(self):
+ i = 0
+ try:
+ while True:
+ v = self[i]
+ yield v
+ i += 1
+ except IndexError:
+ return
+
+ 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(str)
+Sequence.register(range)
+
+
+class ByteString(Sequence):
+
+ """This unifies bytes and bytearray.
+
+ XXX Should add all their methods.
+ """
+
+ByteString.register(bytes)
+ByteString.register(bytearray)
+
+
+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)
+ return self
+
+MutableSequence.register(list)
+MutableSequence.register(bytearray) # Multiply inheriting, see ByteString