How to Sum Dict Elements

How to sum all the values in a dictionary?

As you'd expect:

sum(d.values())

How to sum dict elements

A little ugly, but a one-liner:

dictf = reduce(lambda x, y: dict((k, v + y[k]) for k, v in x.iteritems()), dict1)

Python: Sum of certain values of a dictionary

You will get that error because the value changes as per its iterator. Inorder to find the sum you need to store and add the values to another variable and then call sum() or you could add it to a new variable.

What the sum() does is take a list and iterate through it. In your code what it is doing is passing the current value in the loop only so 1 value.

Example: Note (There are many ways to do this.)

name = "ABC"
sum = 0
for character in name:
    for key, value in dict.items():
        if key == character:
            print(value)
            sum = value + sum

print(sum) 

Python - sum values in dictionary

sum(item['gold'] for item in myList)

How to sum values in multidimensional dictionary?

To sum values for a single subkey you could use sum() with a generator expression:

>>> d = {'A': {'val1': 3,'val2': 5}, 'B': {'val1': 2, 'val2': 6}}
>>> sum(x['val1'] for x in d.values())
5

To sum values for all subkeys you can use collections.Counter:

>>> from collections import Counter
>>> counter = sum(map(Counter, d.values()), Counter())
>>> dict(counter)
{'val2': 11, 'val1': 5}

Sum the values of dictionaries inside a list where the keys are the same

IIUC this is pretty straight forward. You just write a function to sum up all values per key. Then apply it to the transposed list of lists of dicts.

def sum_by_key(dicts):
    result = {}

    for d in dicts:
        for k, v in d.items():
            result[k] = result.get(k, 0) + v

    return result

lists_of_dicts = [[{1:2, 3:4}, {1:10, 2:9}], [{3:8, 2:4}, {3:1, 2:5}]]
result = [sum_by_key(dicts) for dicts in zip(*lists_of_dicts)]

print(result)

(lists_of_dicts would be [A, B, C, D] with your variables)

Output:

[{1: 2, 3: 12, 2: 4}, {1: 10, 2: 14, 3: 1}]

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edit: with your new sample data

lists_of_dicts = [A, B, C, D]
result = [sum_by_key(dicts) for dicts in zip(*lists_of_dicts)]
print(result)

produces

[{'1': 1158, '2': 1450, '3': 542, '4': 2060}, {'1': 702, '2': 2600, '3': 1169, '4': 1670}, {'1': 880, '2': 2480, '3': 2000, '4': 3852}, {'1': 600, '2': 640, '3': 1142, '4': 6230}]

how can I sum values in a dictionary based on just one element of the tuple in the keys?

Use sum() on dictionary values where first item of tuple is 'B'

(Edited as per @rafaelc): Cleaner to not use the ternary operator here

sum(val for key, val in dict.items() if key[0] == 'B')

Instead of original:

 sum(val if key[0] == 'B' else 0 for key, val in dict.items())

Also, refrain from calling your dictionary as dict

How to sum values in dictionary based on position?

You can use the zip() function

aa = {"A": [0, 0.12, 0, 0.73, 0], "B": [0.96, 0, 0.30, 0, 0], "C": [0, 0, 0, 0.11, 0], "D": [0, 0.07, 0, 0.42, 0]}
bb = []

for value in (zip(*list(aa.values()))):
           bb.append(sum(value))

print (bb)  

output :

 [0.96, 0.19, 0.3, 1.26, 0]

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