如何在Python中对具有相同名称的元组的值求和

问题描述

我有以下列表，其中包含必须值的元组:

I have the following list containing tuples that have to values:

mylist=[(3, 'a'), (2, 'b'), (4, 'a'), (5, 'c'), (2, 'a'), (1, 'b')]

有没有办法对所有同名的值求和?比如:

Is there a way to sum all values that share the same name? Something like:

(9, 'a'), (3, 'b'), (5, 'c')

我尝试使用 for 循环迭代元组，但无法得到我想要的.

I tried iterating tuples with for loop but can't get what i want.

谢谢

推荐答案

你可以使用itertools.groupby(按每个元组的第二个值排序后)创建组.然后对于每个组，对每个元组中的第一个元素求和，然后在列表推导中为每个组创建一个元组.

You can use itertools.groupby (after sorting by the second value of each tuple) to create groups. Then for each group, sum the first element in each tuple, then create a tuple per group in a list comprehension.

>>> import itertools
>>> [(sum(i[0] for i in group), key) for key, group in itertools.groupby(sorted(mylist, key = lambda i: i[1]), lambda i: i[1])]
[(9, 'a'), (3, 'b'), (5, 'c')]

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