python中setindex_PythonOrderedSet与.index（）方法

Does anyone know about a fast OrderedSet implementation for python that:

remembers insertion order

has an index() method (like the one lists offer)

All implementations I found are missing the .index() method.

解决方案

You can always add it in a subclass. Here is a basic implementation for the OrderedSet you linked in a comment:

class IndexOrderedSet(OrderedSet):

def index(self, elem):

if key in self.map:

return next(i for i, e in enumerate(self) if e &＃61;&＃61; elem)

else:

raise KeyError("That element isn&＃39;t in the set")

You mentioned you only need add, index, and in-order iteration. You can get this by using an OrderedDict as storage. As a bonus, you can subclass the collections.Set abstract class to get the other set operations frozensets support:

from itertools import count, izip

from collections import OrderedDict, Set

class IndexOrderedSet(Set):

"""An OrderedFrozenSet-like object

Allows constant time &＃39;index&＃39;ing

But doesn&＃39;t allow you to remove elements"""

def __init__(self, iterable &＃61; ()):

self.num &＃61; count()

self.dict &＃61; OrderedDict(izip(iterable, self.num))

def add(self, elem):

if elem not in self:

self.dict[elem] &＃61; next(self.num)

def index(self, elem):

return self.dict[elem]

def __contains__(self, elem):

return elem in self.dict

def __len__(self):

return len(self.dict)

def __iter__(self):

return iter(self.dict)

def __repr__(self):

return &＃39;IndexOrderedSet({})&＃39;.format(self.dict.keys())

You can&＃39;t subclass collections.MutableSet because you can&＃39;t support removing elements from the set and keep the indexes correct.