Python – Pair lists elements to Dictionary

Sometimes, while working with records we can have problem in which we can have pair of lists, we need to pair similar like elements to single key value dictionary. This is very peculiar problem but can have applications in data domains. Lets discuss certain ways in which this task can be performed.

Method #1 : Using loop + extend() + enumerate()
The combination of above functionalities can be employed to solve this question. In this, we iterate for the lists and append like elements to similar key using extend().

# Python3 code to demonstrate working of
# Pair lists elements to Dictionary
# Using loop + extend() + enumerate()

# initializing lists
test_list1 = [1, 2, 3, 1, 1, 2, 3]
test_list2 = [[4, 5], [6, 7], [2, 3], [10, 12],
                 [56, 43], [98, 100], [0, 13]]

# printing original lists
print("The original list 1 is : " + str(test_list1))
print("The original list 2 is : " + str(test_list2))

# Pair lists elements to Dictionary
# Using loop + extend() + enumerate()
res = dict()
for idx, val in enumerate(test_list1):
    if val in res:
        res[val].extend(list(test_list2[idx]))
    else:
        res[val] = list(test_list2[idx])

# printing result
print("The Like elements compiled Dictionary is : " + str(res))

Output :

The original list 1 is : [1, 2, 3, 1, 1, 2, 3]
The original list 2 is : [[4, 5], [6, 7], [2, 3], [10, 12], [56, 43], [98, 100], [0, 13]]
The Like elements compiled Dictionary is : {1: [4, 5, 10, 12, 56, 43], 2: [6, 7, 98, 100], 3: [2, 3, 0, 13]}

Method #2 : Using defaultdict() + zip()
The combination of above tasks can also be used to solve this problem. In this, we pair elements using zip() and initialize the dictionary values as a list to avoid testing for existence of first value.

# Python3 code to demonstrate working of
# Pair lists elements to Dictionary
# Using defaultdict() + zip()
from collections import defaultdict

# initializing lists
test_list1 = [1, 2, 3, 1, 1, 2, 3]
test_list2 = [[4, 5], [6, 7], [2, 3], [10, 12],
                 [56, 43], [98, 100], [0, 13]]

# printing original lists
print("The original list 1 is : " + str(test_list1))
print("The original list 2 is : " + str(test_list2))

# Pair lists elements to Dictionary
# Using defaultdict() + zip()
res = defaultdict(list)
for ele1, ele2 in zip(test_list1, test_list2):
    res[ele1].extend(ele2)

# printing result
print("The Like elements compiled Dictionary is : " + str(dict(res)))

Output :

The original list 1 is : [1, 2, 3, 1, 1, 2, 3]
The original list 2 is : [[4, 5], [6, 7], [2, 3], [10, 12], [56, 43], [98, 100], [0, 13]]
The Like elements compiled Dictionary is : {1: [4, 5, 10, 12, 56, 43], 2: [6, 7, 98, 100], 3: [2, 3, 0, 13]}