在字符串为元组的列表中对相同项的值求和 [英] To sum up values of same items in a list of tuples while they are string

问题描述

如果我有这样的元组列表:

If I have list of tuples like this:

my_list = [('books', '$5'), ('books', '$10'), ('ink', '$20'), ('paper', '$15'), ('paper', '$20'), ('paper', '$15')] 

我如何将列表转到此:

[('books', '$15'), ('ink', '$20'), ('paper', '$50')]

即当两个项目都是元组中的字符串时，添加相同项目的费用.我有价格项目是字符串的问题.任何提示将不胜感激.非常感谢！

i.e. to add the expense of same item while both the items are string in the tuples. I have problem with the price items being string. Any hint would be greatly appreciated. Thanks a lot!

我以这种方式获得第一张清单:

I am getting the first list in this way:

my_list=[]
for line in data:
        item, price  = line.strip('\n').split(',') 
        cost = ["{:s}".format(item.strip()), "${:.2f}".format(float(price))]
        my_list.append(tuple(cost))

现在my_list应该看起来像上面给出的那样.

Now my_list should look like given above.

推荐答案

您可以使用

You can use defaultdict to do this:

>>> from collections import defaultdict
>>> my_list = [('books', '$5'), ('books', '$10'), ('ink', '$20'), ('paper', '$15'), ('paper', '$20'), ('paper', '$15')] 
>>> res = defaultdict(list)
>>> for item, price in my_list:
...     res[item].append(int(price.strip('$')))
... 
>>> total = [(k, "${}".format(sum(v))) for k, v in res.items()]
>>> total
[('ink', '$20'), ('books', '$15'), ('paper', '$50')]

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