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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.
+# Copyright 2009 Raymond Hettinger, released under the MIT License.
+# http://code.activestate.com/recipes/576693/
+
+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)