Why am I getting "None" after merging two dictionaries

Question

I have the following Python script where I merge two dictionaries:

dict1 = {'bookA': 1, 'bookB': 2, 'bookC': 3}
dict2 = {'bookC': 2, 'bookD': 4, 'bookE': 5}
print dict2.update(dict1)

Why do I get as output None rather than the merged dictionaries? How can I display the result?

Thanks.

Because `dict.update()` works in-place and doesn't return a new dictionary object. — Mazdak, Mar 23 '16 at 11:43

score 2 · Accepted Answer · answered Mar 23 '16 at 11:46

2

update does not return a new dictionary. Do this instead:

dict1 = {'bookA': 1, 'bookB': 2, 'bookC': 3}
dict2 = {'bookC': 2, 'bookD': 4, 'bookE': 5}
dict2.update(dict1)
print(dict2)

answered Mar 23 '16 at 11:46

rishabsaraf93

score 1 · Answer 2 · answered Mar 23 '16 at 11:44

1

dict2.update(dict1) updates dict2, but doesn't return it. Use print dict2 instead.

answered Mar 23 '16 at 11:44

Mikhail Gerasimov

2 Answers2