Merge two objects in Python

Question

Is there a good way to merge two objects in Python? Like a built-in method or fundamental library call?

Right now I have this, but it seems like something that shouldn't have to be done manually:

def add_obj(obj, add_obj):

    for property in add_obj:
        obj[property] = add_obj[property]

Note: By "object", I mean a "dictionary": obj = {}

all objects do not have the [] accessor. Are you refering to dictionnaries? — Simon Bergot, Feb 12 '13 at 18:46
Possible duplicate of [How to merge two Python dictionaries in a single expression?](https://stackoverflow.com/questions/38987/how-to-merge-two-python-dictionaries-in-a-single-expression) — Rotareti, Jun 13 '17 at 13:09
The title is misleading. It should be: *Merge two dictionaries in Python*. — Rotareti, Jun 13 '17 at 13:14

score 89 · Accepted Answer · answered Feb 12 '13 at 18:50

89

If obj is a dictionary, use its update function:

obj.update(add_obj)

answered Feb 12 '13 at 18:50

phihag

7

be very careful, as you are updating `obj` in-place; I would rather go with @Anony-Mousse answer – averasko Dec 04 '18 at 16:55

score 34 · Answer 2 · answered Feb 12 '13 at 18:49

34

How about

merged = dict()
merged.update(obj)
merged.update(add_obj)

Note that this is really meant for dictionaries.

If obj already is a dictionary, you can use obj.update(add_obj), obviously.

answered Feb 12 '13 at 18:49

score 1 · Answer 3 · answered Jul 15 '20 at 15:00

1

>>> A = {'a': 1}
>>> B = {'b': 2}
>>> A.update(B)
>>> A
{'a': 1, 'b': 2}

on matching keys:

>>> C = {'a': -1}
>>> A.update(C)
>>> A
{'a': -1, 'b': 2}

answered Jul 15 '20 at 15:00

diogo

3 Answers3