Compare two defaultdictionaries Python

Question

Is there a more efficient way to compare two dictionaries than a double loop ?

for i in d:
    for i2 in d2:
        if i == i2:
            key1 = d.get(i)
            key2 = d2.get(i2)
            print("First key:", key1)
            print("Second key:", key2)

Answer 1

You can get the intersection of the keys by using dictionary views. These operate as sets, meaning you can generate their intersection with &.

Python 2:

for key in d.viewkeys() & d2.viewkeys():
    value1 = d[key]
    value2 = d2[key]

Python 3:

for key in d.keys() & d2.keys():
    value1 = d[key]
    value2 = d2[key]

Even if you didn't have dictionary views, you didn't need to use a double loop. All you needed to do was to test if the key was present:

for key in d:
    if key in d2:
        value1 = d[key]
        value2 = d2[key]