How to construct a dictionary from two dictionaries in python?

Question

Let's say I have a dictionary:

x = {"x1":1,"x2":2,"x3":3}

and I have another dictionary:

y = {"y1":1,"y2":2,"y3":3}

Is there any neat way to constract a 3rd dictionary from the previous two:

z = {"y1":1,"x2":2,"x1":1,"y2":2}

Sorry, I might didn't explain very well. I don't want to add the whole two dictionaries to make new one. I just want some keys from the first one and some other keys from the second one then create a new dictionary — Mero, Dec 04 '13 at 11:50

Kobi K · Answer 1 · 2013-12-04T12:00:10.183

9

If you want the whole 2 dicts:

x = {"x1":1,"x2":2,"x3":3}
y = {"y1":1,"y2":2,"y3":3}


z = dict(x.items() + y.items())
print z

Output:

{'y2': 2, 'y1': 1, 'x2': 2, 'x3': 3, 'y3': 3, 'x1': 1}

If you want the partial dict:

x = {"x1":1,"x2":2,"x3":3}
y = {"y1":1,"y2":2,"y3":3}

keysList = ["x2", "x1", "y1", "y2"]
z = {}

for key, value in dict(x.items() + y.items()).iteritems():
    if key in keysList:
        z.update({key: value})

print z

Output

{'y1': 1, 'x2': 2, 'x1': 1, 'y2': 2}

edited Dec 04 '13 at 12:00

answered Dec 04 '13 at 11:45

Kobi K

7,743
6
42
86

1

First solution will work in python2, but not in python3 – J punto Marcos Mar 03 '16 at 09:35
@JpuntoMarcos You are right (an old answer), You can use `z = dict(list(x.items()) + list(y.items()))` for python3 but keep in mind it's more expensive. – Kobi K Mar 03 '16 at 12:32

score 7 · Answer 2 · answered Dec 04 '13 at 11:44

7

You can use copy for x then update to add the keys and values from y:

z = x.copy()
z.update(y)

answered Dec 04 '13 at 11:44

jonrsharpe

115,751
26
228
437

score 2 · Answer 3 · answered Dec 04 '13 at 12:13

2

Try something like this:

dict([(key, d[key]) for d in [x,y] for key in d.keys() if key not in ['x3', 'y3']])
{'x2': 2, 'y1': 1, 'x1': 1, 'y2': 2}

answered Dec 04 '13 at 12:13

vahid abdi

9,636
4
29
35

How to construct a dictionary from two dictionaries in python?

3 Answers3