odict.py

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# Downloaded from http://code.activestate.com/recipes/576693/
# Licensed under the MIT License

# 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)