91 lines
3 KiB
Python
91 lines
3 KiB
Python
|
# From: https://github.com/ActiveState/code/blob/master/recipes/Python/576696_OrderedSet_with_Weakrefs/ # noqa
|
||
|
|
|
||
|
|
from weakref import proxy
|
||
|
|
|
||
|
|
try:
|
||
|
|
import collections.abc as collections_abc
|
||
|
|
except ImportError:
|
||
|
|
import collections as collections_abc
|
||
|
|
|
||
|
|
|
||
|
|
class Link(object):
|
||
|
|
__slots__ = 'prev', 'next', 'key', '__weakref__'
|
||
|
|
|
||
|
|
|
||
|
|
class OrderedSet(collections_abc.MutableSet):
|
||
|
|
'Set the remembers the order elements were added'
|
||
|
|
# Big-O running times for all methods are the same as for regular sets.
|
||
|
|
# 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). The prev/next links are weakref proxies (to prevent circular
|
||
|
|
# references). Individual links are kept alive by the hard reference in
|
||
|
|
# self.__map. Those hard references disappear when a key is deleted from
|
||
|
|
# an OrderedSet.
|
||
|
|
|
||
|
|
def __init__(self, iterable=None):
|
||
|
|
self.__root = root = Link() # sentinel node for doubly linked list
|
||
|
|
root.prev = root.next = root
|
||
|
|
self.__map = {} # key --> link
|
||
|
|
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):
|
||
|
|
# Store new key in a new link at the end of the linked list
|
||
|
|
if key not in self.__map:
|
||
|
|
self.__map[key] = link = Link()
|
||
|
|
root = self.__root
|
||
|
|
last = root.prev
|
||
|
|
link.prev, link.next, link.key = last, root, key
|
||
|
|
last.next = root.prev = proxy(link)
|
||
|
|
|
||
|
|
def discard(self, key):
|
||
|
|
# Remove an existing item using self.__map to find the link which is
|
||
|
|
# then removed by updating the links in the predecessor and successors.
|
||
|
|
if key in self.__map:
|
||
|
|
link = self.__map.pop(key)
|
||
|
|
link.prev.next = link.next
|
||
|
|
link.next.prev = link.prev
|
||
|
|
|
||
|
|
def __iter__(self):
|
||
|
|
# Traverse the linked list in order.
|
||
|
|
root = self.__root
|
||
|
|
curr = root.next
|
||
|
|
while curr is not root:
|
||
|
|
yield curr.key
|
||
|
|
curr = curr.next
|
||
|
|
|
||
|
|
def __reversed__(self):
|
||
|
|
# Traverse the linked list in reverse order.
|
||
|
|
root = self.__root
|
||
|
|
curr = root.prev
|
||
|
|
while curr is not root:
|
||
|
|
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 __str__(self):
|
||
|
|
return self.__repr__()
|
||
|
|
|
||
|
|
def __eq__(self, other):
|
||
|
|
if isinstance(other, OrderedSet):
|
||
|
|
return len(self) == len(other) and list(self) == list(other)
|
||
|
|
return not self.isdisjoint(other)
|