Python merge dictionaries with custom merge function

Question

I want to merge two dictionaries A and B such that the result contains:

• All pairs from A where key is unique to A
• All pairs from B where key is unique

Answer 1

Stealing this (A.get(k, B.get(k)) snippet from @MartijnPieters

>>> def f(x, y):
        return x * y

>>> A = {1:1, 2:3}
>>> B = {7:3, 2:2}
>>> {k: f(A[k], B[k]) if k in A and k in B else A.get(k, B.get(k))
     for k in A.viewkeys() | B.viewkeys()}
{1: 1, 2: 6, 7: 3}