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Use weakrefs for both forward and backward links.

This commit is contained in:
Raymond Hettinger 2010-09-12 18:13:46 +00:00
parent b084b48cec
commit c5c29c0ac0
1 changed files with 4 additions and 3 deletions
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7
Lib/collections.py
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@ -31,7 +31,9 @@ class OrderedDict(dict, MutableMapping):
# The internal self.__map dictionary maps keys to links in a doubly linked list. # 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 circular doubly linked list starts and ends with a sentinel element.
# The sentinel element never gets deleted (this simplifies the algorithm). # The sentinel element never gets deleted (this simplifies the algorithm).
# The back links are weakref proxies (to prevent circular references). # 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 OrderedDict.
def __init__(self, *args, **kwds): def __init__(self, *args, **kwds):
'''Initialize an ordered dictionary. Signature is the same as for '''Initialize an ordered dictionary. Signature is the same as for
@ -60,8 +62,7 @@ class OrderedDict(dict, MutableMapping):
root = self.__root root = self.__root
last = root.prev last = root.prev
link.prev, link.next, link.key = last, root, key link.prev, link.next, link.key = last, root, key
last.next = link last.next = root.prev = proxy(link)
root.prev = proxy(link)
dict.__setitem__(self, key, value) dict.__setitem__(self, key, value)
def __delitem__(self, key, dict_delitem=dict.__delitem__): def __delitem__(self, key, dict_delitem=dict.__delitem__):