基于元组第一个值的python sum元组列表 [英] python sum tuple list based on tuple first value

问题描述

假设我有以下列表元组:

Suppose I have the following list tuples:

myList = [(0,2),(1,3),(2,4),(0,5),(1,6)]

我想基于相同的第一个元组值对该列表求和:

I want to sum this list based on the same first tuple value:

[(n,m),(n,k),(m,l),(m,z)] = m*k + l*z

对于myList

sum = 2*5 + 3*6 = 28

我怎么能得到这个?

推荐答案

您可以使用collections.defaultdict:

>>> from collections import defaultdict
>>> from operator import mul
>>> lis = [(0,2),(1,3),(2,4),(0,5),(1,6)]
>>> dic = defaultdict(list)
>>> for k,v in lis:
    dic[k].append(v)  #use the first item of the tuple as key and append second one to it
...     

#now multiply only those lists which contain more than 1 item and finally sum them.
>>> sum(reduce(mul,v) for k,v in dic.items() if len(v)>1)
 28

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