Creating a dictionary from 2 lists with duplicate keys

Question

Though I have seen versions of my issue whereby a dictionary was created from two lists (one list with the keys, and the other with the corresponding values), I want to crea

Answer 1

As already mentioned, your desired output is not possible as dictionary keys must be unique.

Below are 2 alternatives if you do not want to lose data.

List of tuples

res = [(i, j) for i, j in zip(keys, values)]

# [(18, [7, 8, 9]),
#  (34, [4, 5, 6]),
#  (30, [1, 2, 3]),
#  (30, [10, 11, 12]),
#  (18, [13, 14, 15])]

Dictionary of lists

from collections import defaultdict

res = defaultdict(list)

for i, j in zip(keys, values):
    res[i].append(j)

# defaultdict(list,
#             {18: [[7, 8, 9], [13, 14, 15]],
#              30: [[1, 2, 3], [10, 11, 12]],
#              34: [[4, 5, 6]]})

Answer 2

Keys need to be unique. 
You Have keys = [18, 34, 30, 30, 18]
Repeated keys 18 and 30 can not be used twice.
Try your script with unique keys and it works fine.
Keys read right to left. Notice you get the first key 18 
and the first key 30, but the second of each key is passed over