Java的TreeSet相当于Python？ [英] Java's TreeSet equivalent in Python?
问题描述
我的问题，
-
是否有可用于Python的等效数据结构？
- Java treeset看起来基本上是一个有序的字典，可以使用某种比较器来实现这种排序。
-
我看到有一个 PEP for Py3K 的OrderedDict，但我使用的是2.6.x.有一些有序的dict实现，特别是可以推荐的？
PS，Just to添加 - 我可以可能导入DictMixin或UserDict并实现我自己的排序/排序字典，并通过比较函数实现 - 但这似乎是过度的。
谢谢。
更新。感谢您的答案。要说明一点，让我说我有一个比较功能，定义如下（给定一个特定的值ln），
def mycmp（x1，y1，ln）：
a = abs（x1-ln）
b = abs（y1-ln）
如果一个< b：
return -1
elif a> b：
返回1
其他：
返回0
我有点不确定我将如何将它整合到有序dict 此处给出的链接.. 。
像
OrderedDict（sorted（d.items（ ），cmp = mycmp（len）））
想法是受欢迎的。
Python 2.7 docs for collections.OrderedDict 有一个 OrderedDict配方。
编辑： 关于排序：使用 key = 而不是 cmp = 。它往往导致更快的代码，而且，在Python3中已经消除了 cmp = 关键字。
d = {
print（d.items（））
＃[（1，2），（3，4），（100 ，101），（5,6），（7,8）]
mycmp 并不清楚您想要作为 x1 传递什么。下面我假定x1应该是每个键值对中的值。如果是这样，你可以这样做：
length = 4
print（sorted（d.items ，key = lambda item：abs（item [1] -length）））
＃[（3，4），（1,2），（5,6），（7,8） 101）]
key = ... 被传递一个函数， lambda项：abs（item [1] -length）。
对于 d.items（）中的每个项目，lambda函数返回数字 abs（item [1] -length）。就排序而言，该数字作为项目的代理。有关Python中排序习语的更多信息，请参阅本文。
PS。 len 是一个Python内置函数。所以，为了不扼杀 len ，我已将变量名称更改为 length 。
I recently came across some Java code that simply put some strings into a Java TreeSet, implemented a distance based comparator for it, and then made its merry way into the sunset to compute a given score to solve the given problem.
My questions,
Is there an equivalent data structure available for Python?
- The Java treeset looks basically to be an ordered dictionary that can use a comparator of some sort to achieve this ordering.
I see there's a PEP for Py3K for an OrderedDict, but I'm using 2.6.x. There are a bunch of ordered dict implementations out there - anyone in particular that can be recommended?
PS, Just to add - I could probably import DictMixin or UserDict and implement my own sorted/ordered dictionary, AND make it happen through a comparator function - but that seems to be overkill.
Thanks.
Update. Thanks for the answers. To elaborate a bit, lets say I've got a compare function thats defined like, (given a particular value ln),
def mycmp(x1, y1, ln):
a = abs(x1-ln)
b = abs(y1-ln)
if a<b:
return -1
elif a>b:
return 1
else:
return 0
I'm a bit unsure about how I'd integrate this into the ordering given in the ordered dict link given here...
Something like,
OrderedDict(sorted(d.items(), cmp=mycmp(len)))
Ideas would be welcome.
The Python 2.7 docs for collections.OrderedDict has a link to a OrderedDict recipe that runs on Python 2.4 or better.
Edit: In regard to sorting: Use key= rather than cmp=. It tends to lead to faster code and moreover, the cmp= keyword has been eliminated in Python3.
d={5:6,7:8,100:101,1:2,3:4}
print(d.items())
# [(1, 2), (3, 4), (100, 101), (5, 6), (7, 8)]
The code you posted for mycmp doesn't make it clear what you want passed as x1. Below, I assume x1 is supposed to be the value in each key-value pair. If so, you could do something like this:
length=4
print(sorted(d.items(),key=lambda item: abs(item[1]-length) ))
# [(3, 4), (1, 2), (5, 6), (7, 8), (100, 101)]
key=... is passed a function, lambda item: abs(item[1]-length).
For each item in d.items(), the lambda function returns the number abs(item[1]-length). This number acts as proxy for the item as far as sorting is concerned. See this essay for more information on sorting idioms in Python.
PS. len is a Python builtin function. So, so as to not clobber that len, I've changed the variable name to length.
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