sum list of dictionary values

Question

I have a list of dictionary in this form :

[
{\'signal_8\': 1, \'signal_1\': 7, \'signal_10\': 5, \'signal_5\': 2, \'signal_2\': 5, \'signal_6\': 3, \'signa         


        

Answer 1

Your current code uses one accumulating sum for all the signals, when instead you need a seperate the sum for each signal.

If you want your original code to work, you need to first check if the key exists in result, and initialise it 0 beforehand if it isn't. Then accumulate the sum for the respective key.

Code:

result = {}
for elm in original_list:
    for k, v in elm.items():

        # Initialise it if it doesn't exist
        if k not in result:
            result[k] = 0

        # accumulate sum seperately 
        result[k] += v

print(result)

Output:

{'signal_9': 12, 'signal_8': 3, 'signal_1': 21, 'signal_3': 18, 'signal_2': 15, 'signal_5': 6, 'signal_4': 27, 'signal_7': 24, 'signal_6': 9, 'signal_10': 15}

Note: As others have shown, to avoid initialising yourself, you can use collections.defaultdict() or collections.Counter() instead.