Sum numbers by letter in list of tuples

Question

I have a list of tuples:

[ (\'A\',100), (\'B\',50), (\'A\',50), (\'B\',20), (\'C\',10) ]

I am trying to sum up all numbers that have the s

Answer 1

>>> from collections import Counter
>>> c = Counter()
>>> for k, num in items:
        c[k] += num


>>> c.items()
[('A', 150), ('C', 10), ('B', 70)]

Less efficient (but nicer looking) one liner version:

>>> Counter(k for k, num in items for i in range(num)).items()
[('A', 150), ('C', 10), ('B', 70)]

Answer 2

In order to achieve this, firstly create a dictionary to store your values. Then convert the dict object to tuple list using .items() Below is the sample code on how to achieve this:

my_list = [ ('A',100), ('B',50), ('A',50), ('B',20), ('C',10) ]
my_dict = {}
for key, val in my_list:
    if key in my_dict:
        my_dict[key] += val
    else:
        my_dict[key] = val

my_dict.items()
# Output: [('A', 150), ('C', 10), ('B', 70)]