Invert python dictionary from {key : [x, y, z]} to {x: key, y : key, z : key}

Question

Sorry, if this one is duplicate, but I am new to python and haven't found solution by googling.

I have a dictionary that looks like:

{
   1 : ['x', 'y'],
   2 : ['z'],
   3 : ['a']
}

All values in lists are guaranteed to be unique. And I want to transform this dictionary to:

{
   'x' : 1,
   'y' : 1,
   'z' : 2,
   'a' : 3
}

What is the most pythonic and clean way to write this?

Remember that this can only work if all values across the lists are unique. Dictionaries require unique keys. — timgeb, Dec 13 '20 at 17:01

score 2 · Accepted Answer · answered Dec 13 '20 at 16:59

2

Try this:

dct = {
   1 : ['x', 'y'],
   2 : ['z'],
   3 : ['a']
}

print({key:val for val, keys in dct.items() for key in keys})

Output:

{'a': 3, 'x': 1, 'y': 1, 'z': 2}

answered Dec 13 '20 at 16:59

dimay

2,768
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score 0 · Answer 2 · answered Dec 13 '20 at 17:01

You can try this.

d = {
1 :['x', 'y'],
2 :['z'],
3 :['a']
}

'''
{
   'x' : 1,
   'y' : 1,
   'z' : 2,
   'a' : 3
}
'''

d2 = {}


for k,v in d.items():
    for i in v:
        d2[i] = k


print(d2)

Output:

{'x': 1, 'y': 1, 'z': 2, 'a': 3}
[Finished in 0.2s]

Invert python dictionary from {key : [x, y, z]} to {x: key, y : key, z : key}

2 Answers2