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How can I update a list of dictionaries with a second list of dictionaries?

So I have been working on this for hours and have scoured many similar questions on Stackoverflow for a response, but no dice. It seems simple enough, but I just can’t seem to get the desired result. I have one list of dictionaries, A, that I would like to merge with another list of dictionaries, B. A and B are the same length. I want a resulting list of dictionaries C that is also the same length such that the key:value pairs in B are appended to the existing key:value pairs in A. An example and unsuccessful attempt to achieve the desired result is below.

A = [{'a':1, 'b':2, 'c':3},{'a':4, 'b':5, 'c':6},{'a':7, 'b':8, 'c':9}]
B = [{'d':10},{'d':11},{'d':12}]

for a in A:
    for b in B:
        C = a.update(b)

print(C)

//Actual output: None
//Desired output: [{'a':1, 'b':2, 'c':3, 'd':10},{'a':4, 'b':5, 'c':6, 'd':11},{'a':7, 'b':8, 'c':9, 'd':12}]

In theory, it seems to me like the above code should work, but it does not. Any help would be greatly appreciated.

Thanks, Aaron

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Answer

Meet zip, it iterates through multiple lists in parallel:

A = [{'a':1, 'b':2, 'c':3},{'a':4, 'b':5, 'c':6},{'a':7, 'b':8, 'c':9}]
B = [{'d':10},{'d':11},{'d':12}]
for a,b in zip(A,B):
  a.update(b)
print(A)
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