pataphor wrote:
Raymond Hettinger wrote:
Right. Here's a link to a weakref version (though I think the
previous __del__ version also does the trick):
http://code.activestate.com/recipes/576696/
Interesting. But how about this one? Does it also have the reference
problem? By the way collections.MutableSet needs python >= 2.6
...
class OrderedSet(collections.MutableSet):
'Set that remembers the order elements were added'
# Big-O running times for all methods are the same as for regular sets.
def __init__(self, iterable=None):
self.__map = {} # key --> [prev,key,next]
if iterable is not None:
self |= iterable
...
def add(self, key):
if not self.__map:
self.start = key
self.__map = {key: [key,key,key]}
...
Two responses:
(1) No, it doesn't have the reference problem, but it does replace
a reference with map lookup (at a performance cost).
and
(2) Why, oh why, do people feel so comforted adding double_underscores
to data structures? If I want to inherit from your mapping in order
to log the attempts to discard a key not actually in the set, I
have to either us the nasty name mangling to get at self.__map, or
name my subclass OrderedSet and take advantage of a not-guaranteed
name mangling. What on earth makes you unwilling to go with "_map"
and credit your code's consumers with a bit of common sense?
Sorry, this latter rant has been building up for a while (spurred on by
a sojourn into the unittest code where they have the private disease in
spades.
--Scott David Daniels
scott.dani...@acm.org
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