Created
October 26, 2012 05:52
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Python: OrderedSet
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class OrderedSet(collections.MutableSet): | |
def __init__(self, iterable=None): | |
self.end = end = [] | |
end += [None, end, end] # sentinel node for doubly linked list | |
self.map = {} # key --> [key, prev, next] | |
if iterable is not None: | |
self |= iterable | |
def __len__(self): | |
return len(self.map) | |
def __contains__(self, key): | |
return key in self.map | |
def add(self, key): | |
if key not in self.map: | |
end = self.end | |
curr = end[PREV] | |
curr[NEXT] = end[PREV] = self.map[key] = [key, curr, end] | |
def discard(self, key): | |
if key in self.map: | |
key, prev, next = self.map.pop(key) | |
prev[NEXT] = next | |
next[PREV] = prev | |
def __iter__(self): | |
end = self.end | |
curr = end[NEXT] | |
while curr is not end: | |
yield curr[KEY] | |
curr = curr[NEXT] | |
def __reversed__(self): | |
end = self.end | |
curr = end[PREV] | |
while curr is not end: | |
yield curr[KEY] | |
curr = curr[PREV] | |
def pop(self, last=True): | |
if not self: | |
raise KeyError('set is empty') | |
key = next(reversed(self)) if last else next(iter(self)) | |
self.discard(key) | |
return key | |
def __repr__(self): | |
if not self: | |
return '%s()' % (self.__class__.__name__,) | |
return '%s(%r)' % (self.__class__.__name__, list(self)) | |
def __eq__(self, other): | |
if isinstance(other, OrderedSet): | |
return len(self) == len(other) and list(self) == list(other) | |
return set(self) == set(other) | |
def __del__(self): | |
self.clear() # remove circular references |
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