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# Backport of OrderedDict() class that runs on Python 2.4, 2.5, 2.6, 2.7 and pypy.

# Passes Python2.7's test suite and incorporates all the latest updates.

try:

    from thread import get_ident as _get_ident

except ImportError:

    from dummy_thread import get_ident as _get_ident

try:

    from _abcoll import KeysView, ValuesView, ItemsView

except ImportError:

    pass

class OrderedDict(dict):

    'Dictionary that remembers insertion order'

    # An inherited dict maps keys to values.

    # The inherited dict provides __getitem__, __len__, __contains__, and get.

    # The remaining methods are order-aware.

    # Big-O running times for all methods are the same as for regular dictionaries.

    # The internal self.__map dictionary maps keys to links in a doubly linked list.

    # The circular doubly linked list starts and ends with a sentinel element.

    # The sentinel element never gets deleted (this simplifies the algorithm).

    # Each link is stored as a list of length three:  [PREV, NEXT, KEY].

    def __init__(self, *args, **kwds):

        '''Initialize an ordered dictionary.  Signature is the same as for

        regular dictionaries, but keyword arguments are not recommended

        because their insertion order is arbitrary.

        '''

        if len(args) > 1:

            raise TypeError('expected at most 1 arguments, got %d' % len(args))

        try:

            self.__root

        except AttributeError:

            self.__root = root = []                     # sentinel node

            root[:] = [root, root, None]

            self.__map = {}

        self.__update(*args, **kwds)

    def __setitem__(self, key, value, dict_setitem=dict.__setitem__):

        'od.__setitem__(i, y) <==> od[i]=y'

        # Setting a new item creates a new link which goes at the end of the linked

        # list, and the inherited dictionary is updated with the new key/value pair.

        if key not in self:

            root = self.__root

            last = root[0]

            last[1] = root[0] = self.__map[key] = [last, root, key]

        dict_setitem(self, key, value)

    def __delitem__(self, key, dict_delitem=dict.__delitem__):

        'od.__delitem__(y) <==> del od[y]'

        # Deleting an existing item uses self.__map to find the link which is

        # then removed by updating the links in the predecessor and successor nodes.

        dict_delitem(self, key)

        link_prev, link_next, key = self.__map.pop(key)

        link_prev[1] = link_next

        link_next[0] = link_prev

    def __iter__(self):

        'od.__iter__() <==> iter(od)'

        root = self.__root

        curr = root[1]

        while curr is not root:

            yield curr[2]

            curr = curr[1]

    def __reversed__(self):

        'od.__reversed__() <==> reversed(od)'

        root = self.__root

        curr = root[0]

        while curr is not root:

            yield curr[2]

            curr = curr[0]

    def clear(self):

        'od.clear() -> None.  Remove all items from od.'

        try:

            for node in self.__map.itervalues():

                del node[:]

            root = self.__root

            root[:] = [root, root, None]

            self.__map.clear()

        except AttributeError:

            pass

        dict.clear(self)

    def popitem(self, last=True):

        '''od.popitem() -> (k, v), return and remove a (key, value) pair.

        Pairs are returned in LIFO order if last is true or FIFO order if false.

        '''

        if not self:

            raise KeyError('dictionary is empty')

        root = self.__root

        if last:

            link = root[0]

            link_prev = link[0]

            link_prev[1] = root

            root[0] = link_prev

        else:

            link = root[1]

            link_next = link[1]

            root[1] = link_next

            link_next[0] = root

        key = link[2]

        del self.__map[key]

        value = dict.pop(self, key)

        return key, value

    # -- the following methods do not depend on the internal structure --

    def keys(self):

        'od.keys() -> list of keys in od'

        return list(self)

    def values(self):

        'od.values() -> list of values in od'

        return [self[key] for key in self]

    def items(self):

        'od.items() -> list of (key, value) pairs in od'

        return [(key, self[key]) for key in self]

    def iterkeys(self):

        'od.iterkeys() -> an iterator over the keys in od'

        return iter(self)

    def itervalues(self):

        'od.itervalues -> an iterator over the values in od'

        for k in self:

            yield self[k]

    def iteritems(self):

        'od.iteritems -> an iterator over the (key, value) items in od'

        for k in self:

            yield (k, self[k])

    def update(*args, **kwds):

        '''od.update(E, **F) -> None.  Update od from dict/iterable E and F.

        If E is a dict instance, does:           for k in E: od[k] = E[k]

        If E has a .keys() method, does:         for k in E.keys(): od[k] = E[k]

        Or if E is an iterable of items, does:   for k, v in E: od[k] = v

        In either case, this is followed by:     for k, v in F.items(): od[k] = v

        '''

        if len(args) > 2:

            raise TypeError('update() takes at most 2 positional '

                            'arguments (%d given)' % (len(args),))

        elif not args:

            raise TypeError('update() takes at least 1 argument (0 given)')

        self = args[0]

        # Make progressively weaker assumptions about "other"

        other = ()

        if len(args) == 2:

            other = args[1]

        if isinstance(other, dict):

            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

    __update = update  # let subclasses override update without breaking __init__

    __marker = object()

    def pop(self, key, default=__marker):

        '''od.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.

        '''

        if key in self:

            result = self[key]

            del self[key]

            return result

        if default is self.__marker:

            raise KeyError(key)

        return default

    def setdefault(self, key, default=None):

        'od.setdefault(k[,d]) -> od.get(k,d), also set od[k]=d if k not in od'

        if key in self:

            return self[key]

        self[key] = default

        return default

    def __repr__(self, _repr_running={}):

        'od.__repr__() <==> repr(od)'

        call_key = id(self), _get_ident()

        if call_key in _repr_running:

            return '...'

        _repr_running[call_key] = 1

        try:

            if not self:

                return '%s()' % (self.__class__.__name__,)

            return '%s(%r)' % (self.__class__.__name__, self.items())

        finally:

            del _repr_running[call_key]

    def __reduce__(self):

        'Return state information for pickling'

        items = [[k, self[k]] for k in self]

        inst_dict = vars(self).copy()

        for k in vars(OrderedDict()):

            inst_dict.pop(k, None)

        if inst_dict:

            return (self.__class__, (items,), inst_dict)

        return self.__class__, (items,)

    def copy(self):

        'od.copy() -> a shallow copy of od'

        return self.__class__(self)

    @classmethod

    def fromkeys(cls, iterable, value=None):

        '''OD.fromkeys(S[, v]) -> New ordered dictionary with keys from S

        and values equal to v (which defaults to None).

        '''

        d = cls()

        for key in iterable:

            d[key] = value

        return d

    def __eq__(self, other):

        '''od.__eq__(y) <==> od==y.  Comparison to another OD is order-sensitive

        while comparison to a regular mapping is order-insensitive.

        '''

        if isinstance(other, OrderedDict):

            return len(self)==len(other) and self.items() == other.items()

        return dict.__eq__(self, other)

    def __ne__(self, other):

        return not self == other

    # -- the following methods are only used in Python 2.7 --

    def viewkeys(self):

        "od.viewkeys() -> a set-like object providing a view on od's keys"

        return KeysView(self)

    def viewvalues(self):

        "od.viewvalues() -> an object providing a view on od's values"

        return ValuesView(self)

    def viewitems(self):

        "od.viewitems() -> a set-like object providing a view on od's items"

        return ItemsView(self)