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

What is generating the list of tuples? Is it you? If so, why not try a defaultdict(list) to append the values to the right letter at the time of making the list of tuples. Then you can simply sum them. See example below.

>>> from collections import defaultdict
>>> val_store = defaultdict(list)
>>> # next lines are me simulating the creation of the tuple
>>> val_store['A'].append(10)
>>> val_store['B'].append(20)
>>> val_store['C'].append(30)
>>> val_store
defaultdict(, {'C': [30], 'A': [10], 'B': [20]})
>>> val_store['A'].append(10)
>>> val_store['C'].append(30)
>>> val_store['B'].append(20)
>>> val_store
defaultdict(, {'C': [30, 30], 'A': [10, 10], 'B': [20, 20]})

>>> for val in val_store:
...   print(val, sum(val_store[val]))
... 
C 60
A 20
B 40