python sum tuple list based on tuple first value -


suppose have following list tuples:

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

i want sum list based on same first tuple value:

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

for mylist

sum = 2*5 + 3*6 = 28

how can got this?

you can use collections.defaultdict:

>>> collections import defaultdict >>> operator import mul >>> lis = [(0,2),(1,3),(2,4),(0,5),(1,6)] >>> dic = defaultdict(list) >>> k,v in lis:     dic[k].append(v)  #use first item of tuple key , append second 1 ...       #now multiply lists contain more 1 item , sum them. >>> sum(reduce(mul,v) k,v in dic.items() if len(v)>1)  28

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