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

user_14830199 0
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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

list sum dictionary python
6 Answers

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)]

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

user_49540370

One possible approach would be:

import pandas as pd
    
flat_list = ['hello,5', 'mellow,4', 'mellow,2', 'yellow,2', 'yellow,7', 'hello,7', 'mellow,7', 'hello,7']
new_list = [v.split(',') for v in flat_list]
    
df = pd.DataFrame(new_list)
df[1] = df[1].astype(int)
df2 = df.groupby(0).sum()
print(df2)

Output:

    0        1
    hello   19
    mellow  13
    yellow   9
user_175618550

You can do this very simply without importing additional modules like so:

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

d = {}
for s in t: #for each string
    w, n = s.split(',') #get the string and the number
    d[w] = d[w] + int(n) if w in d.keys() else int(n) #add the number (sum)

l = list(d.items()) #make the result a list of tuples
print(l)

Output:

[('hello', 19), ('mellow', 13), ('yellow', 9)]
user_176679140

the last sum up does not work and i do not get my desired output

Actually it works fine, you just forgot to combine the two lists. Add

print(list(zip(val, va)))

and you'll see:

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

That's equivalent to your desired output:

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

Only the entries for yellow and mellow are in different order, since mellow appears first in the input.

user_126710570

Summarising the replies above I'd say that the cleanest way, without the need of external imports, seems to be:

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

d = {}
for ele in flat_list:
    key, value = ele.split(',')
    d[key]= d.get(key, 0) + int(value)
    
list(d.items())

And the output is:

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

That can be sorted by increasing value like this (or alphabetically using x[0]; set reverse to True for descending order):

sorted(list(d.items()), key=lambda x: x[1], reverse=False)
user_75648090

for some reason the last sum up does not work

To fix your original solution:

d = {ka:sum([int(x) for x in va]) for ka,va in d.items()}
user_28237550
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