分组Python元组列表 [英] Grouping Python tuple list

问题描述

我有一个这样的(标签，计数)元组列表:

I have a list of (label, count) tuples like this:

[('grape', 100), ('grape', 3), ('apple', 15), ('apple', 10), ('apple', 4), ('banana', 3)]

由此，我想对所有具有相同标签的值求和(相同的标签始终相邻)，并以相同的标签顺序返回列表:

From that I want to sum all values with the same label (same labels always adjacent) and return a list in the same label order:

[('grape', 103), ('apple', 29), ('banana', 3)]

我知道我可以用类似的方法解决它:

I know I could solve it with something like:

def group(l):
    result = []
    if l:
        this_label = l[0][0]
        this_count = 0
        for label, count in l:
            if label != this_label:
                result.append((this_label, this_count))
                this_label = label
                this_count = 0
            this_count += count
        result.append((this_label, this_count))
    return result

但是，有没有更Pythonic/优雅/有效的方式来做到这一点?

But is there a more Pythonic / elegant / efficient way to do this?

推荐答案

itertools.groupby可以做您想做的事情:

itertools.groupby can do what you want:

import itertools
import operator

L = [('grape', 100), ('grape', 3), ('apple', 15), ('apple', 10),
     ('apple', 4), ('banana', 3)]

def accumulate(l):
    it = itertools.groupby(l, operator.itemgetter(0))
    for key, subiter in it:
       yield key, sum(item[1] for item in subiter) 

>>> print list(accumulate(L))
[('grape', 103), ('apple', 29), ('banana', 3)]
>>> 

这篇关于分组Python元组列表的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！