Adding dictionaries together Python

Question

I have two dictionaries and I d like to be able to make them one   Something like this pseudo-Python would be nice   dic0     dic0   0  dic1     dic1   1   ndic   dic0   dic1   ndic would equal   dic0   0   dic1   1

User · Answer

Here are quite a few ways to add dictionaries.

You can use Python3's dictionary unpacking feature.

ndic = {**dic0, **dic1}

Or create a new dict by adding both items.

ndic = dict(dic0.items() + dic1.items())

If your ok to modify dic0

dic0.update(dic1)

If your NOT ok to modify dic0

ndic = dic0.copy()
ndic.update(dic1)

If all the keys in one dict are ensured to be strings (dic1 in this case, of course args can be swapped)

ndic = dict(dic0, **dic1)

In some cases it may be handy to use dict comprehensions (Python 2.7 or newer),
Especially if you want to filter out or transform some keys/values at the same time.

ndic = {k: v for d in (dic0, dic1) for k, v in d.items()}

User · Answer

gt  gt  gt  dic0     dic0  0   gt  gt  gt  dic1     dic1  1   gt  gt  gt  ndic   dict dic0 items     dic1 items     gt  gt  gt  ndic   dic0   0   dic1   1   gt  gt  gt

User · Answer

dic0 update dic1    Note this doesn t actually return the combined dictionary  it just mutates dic0

User · Answer

Please search the site before asking questions next time  how to concatenate two dictionaries to create a new one in Python   The easiest way to do it is to simply use your example code  but using the items   member of each dictionary  So  the code would be   dic0     dic0   0  dic1     dic1   1  dic2   dict dic0 items     dic1 items      I tested this in IDLE and it works fine   However  the previous question on this topic states that this method is slow and chews up memory  There are several other ways recommended there  so please see that if memory usage is important

User · Answer

You are looking for the update method  dic0 update  dic1   print  dic0      gives    dic0   0   dic1   1

User · Answer

If you re interested in creating a new dict without using intermediary storage   this is faster  and in my opinion  cleaner than using dict items     dic2   dict dic0    dic1    Or if you re happy to use one of the existing dicts   dic0 update dic1

[python] Adding dictionaries together, Python

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