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

def merge_dict(dict1,dict2):
    dict1={1:'red'}
    dict2={2:'black',3:'yellow'}
    dict1.update(dict2)
    print 'dict3 =',dict1

merge_dict(dict1,dict2)

Output:

dict3 = {1: 'red', 2: 'black', 3: 'yellow'}

Answer 2

>>> def f(x,y):
...     return x*y
... 
>>> dict([(k,v) for k,v in A.items()] + [ (k,v) if k not in A else (k,f(A[k],B[k])) for k,v in B.items()])
{1: 1, 2: 6, 7: 3}