# Source code for _abcoll

    # 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 certain
    bootstrapping issues.  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",
               ]

    ### ONE-TRICK PONIES ###

    def _hasattr(C, attr):
        try:
            return any(attr in B.__dict__ for B in C.__mro__)
        except AttributeError:
            # Old-style class
            return hasattr(C, attr)

    class Hashable:
        __metaclass__ = ABCMeta

        @abstractmethod
        def __hash__(self):
            return 0

        @classmethod
        def __subclasshook__(cls, C):
            if cls is Hashable:
                try:
                    for B in C.__mro__:
                        if "__hash__" in B.__dict__:
                            if B.__dict__["__hash__"]:
                                return True
                            break
                except AttributeError:
                    # Old-style class
                    if getattr(C, "__hash__", None):
                        return True
            return NotImplemented

    class Iterable:
        __metaclass__ = ABCMeta

        @abstractmethod
        def __iter__(self):
            while False:
                yield None

        @classmethod
        def __subclasshook__(cls, C):
            if cls is Iterable:
                if _hasattr(C, "__iter__"):
                    return True
            return NotImplemented

    Iterable.register(str)

    class Iterator(Iterable):

        @abstractmethod
        def next(self):
            'Return the next item from the iterator. When exhausted, raise StopIteration'
            raise StopIteration

        def __iter__(self):
            return self

        @classmethod
        def __subclasshook__(cls, C):
            if cls is Iterator:
                if _hasattr(C, "next") and _hasattr(C, "__iter__"):
                    return True
            return NotImplemented

    class Sized:
        __metaclass__ = ABCMeta

        @abstractmethod
        def __len__(self):
            return 0

        @classmethod
        def __subclasshook__(cls, C):
            if cls is Sized:
                if _hasattr(C, "__len__"):
                    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 _hasattr(C, "__contains__"):
                    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 _hasattr(C, "__call__"):
                    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), redefine __le__ and __ge__,
        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 len(self) > len(other) and self.__ge__(other)

        def __ge__(self, other):
            if not isinstance(other, Set):
                return NotImplemented
            if len(self) < len(other):
                return False
            for elem in other:
                if elem not in self:
                    return False
            return True

        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)

        __rand__ = __and__

        def isdisjoint(self, other):
            'Return True if two sets have a null intersection.'
            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)

        __ror__ = __or__

        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 __rsub__(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 other
                                       if value not in self)

        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)

        __rxor__ = __xor__

        # Sets are not hashable by default, but subclasses can change this
        __hash__ = None

        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):
        """A mutable set is a finite, iterable container.

        This class provides concrete generic implementations of all
        methods except for __contains__, __iter__, __len__,
        add(), and discard().

        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 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):

        """A Mapping is a generic container for associating key/value
        pairs.

        This class provides concrete generic implementations of all
        methods except for __getitem__, __iter__, and __len__.

        """

        @abstractmethod
        def __getitem__(self, key):
            raise KeyError

        def get(self, key, default=None):
            'D.get(k[,d]) -> D[k] if k in D, else d.  d defaults to None.'
            try:
                return self[key]
            except KeyError:
                return default

        def __contains__(self, key):
            try:
                self[key]
            except KeyError:
                return False
            else:
                return True

        def iterkeys(self):
            'D.iterkeys() -> an iterator over the keys of D'
            return iter(self)

        def itervalues(self):
            'D.itervalues() -> an iterator over the values of D'
            for key in self:
                yield self[key]

        def iteritems(self):
            'D.iteritems() -> an iterator over the (key, value) items of D'
            for key in self:
                yield (key, self[key])

        def keys(self):
            "D.keys() -> list of D's keys"
            return list(self)

        def items(self):
            "D.items() -> list of D's (key, value) pairs, as 2-tuples"
            return [(key, self[key]) for key in self]

        def values(self):
            "D.values() -> list of D's values"
            return [self[key] for key in self]

        # Mappings are not hashable by default, but subclasses can change this
        __hash__ = None

        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

    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])

    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]

    class MutableMapping(Mapping):

        """A MutableMapping is a generic container for associating
        key/value pairs.

        This class provides concrete generic implementations of all
        methods except for __getitem__, __setitem__, __delitem__,
        __iter__, and __len__.

        """

        @abstractmethod
        def __setitem__(self, key, value):
            raise KeyError

        @abstractmethod
        def __delitem__(self, key):
            raise KeyError

        __marker = object()

        def pop(self, key, default=__marker):
            '''D.pop(k[,d]) -> v, remove specified key and return the corresponding value.
              If key is not found, d is returned if given, otherwise KeyError is raised.
            '''
            try:
                value = self[key]
            except KeyError:
                if default is self.__marker:
                    raise
                return default
            else:
                del self[key]
                return value

        def popitem(self):
            '''D.popitem() -> (k, v), remove and return some (key, value) pair
               as a 2-tuple; but raise KeyError if D is empty.
            '''
            try:
                key = next(iter(self))
            except StopIteration:
                raise KeyError
            value = self[key]
            del self[key]
            return key, value

        def clear(self):
            'D.clear() -> None.  Remove all items from D.'
            try:
                while True:
                    self.popitem()
            except KeyError:
                pass

        def update(*args, **kwds):
            ''' D.update([E, ]**F) -> None.  Update D from mapping/iterable E and F.
                If E present and has a .keys() method, does:     for k in E: D[k] = E[k]
                If E present and lacks .keys() method, does:     for (k, v) in E: D[k] = v
                In either case, this is followed by: for k, v in F.items(): D[k] = v
            '''
            if not args:
                raise TypeError("descriptor 'update' of 'MutableMapping' object "
                                "needs an argument")
            self = args[0]
            args = args[1:]
            if len(args) > 1:
                raise TypeError('update expected at most 1 arguments, got %d' %
                                len(args))
            if args:
                other = args[0]
                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):
            'D.setdefault(k[,d]) -> D.get(k,d), also set D[k]=d if k not in D'
            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):
            '''S.index(value) -> integer -- return first index of value.
               Raises ValueError if the value is not present.
            '''
            for i, v in enumerate(self):
                if v == value:
                    return i
            raise ValueError

        def count(self, value):
            'S.count(value) -> integer -- return number of occurrences of value'
            return sum(1 for v in self if v == value)

    Sequence.register(tuple)
    Sequence.register(basestring)
    Sequence.register(buffer)
    Sequence.register(xrange)

    class MutableSequence(Sequence):

        """All the operations on a read-only sequence.

        Concrete subclasses must provide __new__ or __init__,
        __getitem__, __setitem__, __delitem__, __len__, and insert().

        """

        @abstractmethod
        def __setitem__(self, index, value):
            raise IndexError

        @abstractmethod
        def __delitem__(self, index):
            raise IndexError

        @abstractmethod
        def insert(self, index, value):
            'S.insert(index, object) -- insert object before index'
            raise IndexError

        def append(self, value):
            'S.append(object) -- append object to the end of the sequence'
            self.insert(len(self), value)

        def reverse(self):
            'S.reverse() -- reverse *IN PLACE*'
            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):
            'S.extend(iterable) -- extend sequence by appending elements from the iterable'
            for v in values:
                self.append(v)

        def pop(self, index=-1):
            '''S.pop([index]) -> item -- remove and return item at index (default last).
               Raise IndexError if list is empty or index is out of range.
            '''
            v = self[index]
            del self[index]
            return v

        def remove(self, value):
            '''S.remove(value) -- remove first occurrence of value.
               Raise ValueError if the value is not present.
            '''
            del self[self.index(value)]

        def __iadd__(self, values):
            self.extend(values)
            return self

    MutableSequence.register(list)