Is there any pythonic way to combine two dicts (adding values for keys that appear in both)?

Question

For example I have two dicts:

Dict A: {\'a\': 1, \'b\': 2, \'c\': 3}
Dict B: {\'b\': 3, \'c\': 4, \'d\': 5}

I need a pythonic way of \'comb

Answer 1

This is a simple solution for merging two dictionaries where += can be applied to the values, it has to iterate over a dictionary only once

a = {'a':1, 'b':2, 'c':3}

dicts = [{'b':3, 'c':4, 'd':5},
         {'c':9, 'a':9, 'd':9}]

def merge_dicts(merged,mergedfrom):
    for k,v in mergedfrom.items():
        if k in merged:
            merged[k] += v
        else:
            merged[k] = v
    return merged

for dct in dicts:
    a = merge_dicts(a,dct)
print (a)
#{'c': 16, 'b': 5, 'd': 14, 'a': 10}