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+# Copyright (c) 2009 Raymond Hettinger
+#
+# Permission is hereby granted, free of charge, to any person
+# obtaining a copy of this software and associated documentation files
+# (the "Software"), to deal in the Software without restriction,
+# including without limitation the rights to use, copy, modify, merge,
+# publish, distribute, sublicense, and/or sell copies of the Software,
+# and to permit persons to whom the Software is furnished to do so,
+# subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be
+# included in all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+# OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+# HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+# WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+# OTHER DEALINGS IN THE SOFTWARE.
+
+from UserDict import DictMixin
+
+class OrderedDict(dict, DictMixin):
+
+ def __init__(self, *args, **kwds):
+ if len(args) > 1:
+ raise TypeError('expected at most 1 arguments, got %d' % len(args))
+ try:
+ self.__end
+ except AttributeError:
+ self.clear()
+ self.update(*args, **kwds)
+
+ def clear(self):
+ self.__end = end = []
+ end += [None, end, end] # sentinel node for doubly linked list
+ self.__map = {} # key --> [key, prev, next]
+ dict.clear(self)
+
+ def __setitem__(self, key, value):
+ if key not in self:
+ end = self.__end
+ curr = end[1]
+ curr[2] = end[1] = self.__map[key] = [key, curr, end]
+ dict.__setitem__(self, key, value)
+
+ def __delitem__(self, key):
+ dict.__delitem__(self, key)
+ key, prev, next = self.__map.pop(key)
+ prev[2] = next
+ next[1] = prev
+
+ def __iter__(self):
+ end = self.__end
+ curr = end[2]
+ while curr is not end:
+ yield curr[0]
+ curr = curr[2]
+
+ def __reversed__(self):
+ end = self.__end
+ curr = end[1]
+ while curr is not end:
+ yield curr[0]
+ curr = curr[1]
+
+ def popitem(self, last=True):
+ if not self:
+ raise KeyError('dictionary is empty')
+ if last:
+ key = reversed(self).next()
+ else:
+ key = iter(self).next()
+ value = self.pop(key)
+ return key, value
+
+ def __reduce__(self):
+ items = [[k, self[k]] for k in self]
+ tmp = self.__map, self.__end
+ del self.__map, self.__end
+ inst_dict = vars(self).copy()
+ self.__map, self.__end = tmp
+ if inst_dict:
+ return (self.__class__, (items,), inst_dict)
+ return self.__class__, (items,)
+
+ def keys(self):
+ return list(self)
+
+ setdefault = DictMixin.setdefault
+ update = DictMixin.update
+ pop = DictMixin.pop
+ values = DictMixin.values
+ items = DictMixin.items
+ iterkeys = DictMixin.iterkeys
+ itervalues = DictMixin.itervalues
+ iteritems = DictMixin.iteritems
+
+ def __repr__(self):
+ if not self:
+ return '%s()' % (self.__class__.__name__,)
+ return '%s(%r)' % (self.__class__.__name__, self.items())
+
+ def copy(self):
+ return self.__class__(self)
+
+ @classmethod
+ def fromkeys(cls, iterable, value=None):
+ d = cls()
+ for key in iterable:
+ d[key] = value
+ return d
+
+ def __eq__(self, other):
+ if isinstance(other, OrderedDict):
+ if len(self) != len(other):
+ return False
+ for p, q in zip(self.items(), other.items()):
+ if p != q:
+ return False
+ return True
+ return dict.__eq__(self, other)
+
+ def __ne__(self, other):
+ return not self == other