python: sum values in a list if they share the first word

Question

I have a list as follows,

flat_list = ['hello,5', 'mellow,4', 'mellow,2', 'yellow,2', 'yellow,7', 'hello,7', 'mellow,7', 'hello,7']

I would like to get the sum of the values if they share the same word, so the output should be,

desired output:

l = [('hello',19), ('yellow', 9), ('mellow',13)]

so far, I have tried the following,

new_list = [v.split(',') for v in flat_list]

d = {}
for key, value in new_list:
   if key not in d.keys():
      d[key] = [key]
   d[key].append(value)

# getting rid of the first key in value lists
val = [val.pop(0) for k,val in d.items()]
# summing up the values
va = [sum([int(x) for x in va]) for ka,va in d.items()]

however for some reason the last sum up does not work and i do not get my desired output

Answer 1

Here is a variant for accomplishing your goal using defaultdict:

from collections import defaultdict

t = ['hello,5', 'mellow,4', 'mellow,2', 'yellow,2',
     'yellow,7', 'hello,7', 'mellow,7', 'hello,7']

count = defaultdict(int)

for name_number in t:
    name, number = name_number.split(",")
    count[name] += int(number)

You could also use Counter:

from collections import Counter

count = Counter()

for name_number in t:
    name, number = name_number.split(",")
    count[name] += int(number)

In both cases you can convert the output to a list of tuples using:

list(count.items())
# -> [('hello', 19), ('mellow', 13), ('yellow', 9)]

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I ran your code and I do get the correct results (although not in your desired format).