Python – Assigning Key values to list elements from Value list Dictionary
Given List of elements, map them with keys of matching value from value list.
Input : test_list = [4, 6, 3, 5, 3], test_dict = {“Gfg” : [5, 3, 6], “is” : [8, 4]}
Output : [‘is’, ‘Gfg’, ‘Gfg’, ‘Gfg’, ‘Gfg’]
Explanation : 4 is present in “is” key, hence mapped in new list.Attention geek! Strengthen your foundations with the Python Programming Foundation Course and learn the basics.
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Input : test_list = [6, 3, 5, 3], test_dict = {“Gfg” : [5, 3, 6], “is” : [18, 14]}
Output : [‘Gfg’, ‘Gfg’, ‘Gfg’, ‘Gfg’]
Explanation : All elements present in “Gfg” key.
Method #1 : Using list comprehension
This is one of the ways in which this task can be performed. In this, we extract each element of dictionary value list to check list value occurrence, if matched, we assign that key’s value to that index.
Python3
# Python3 code to demonstrate working of # Assigning Key values to list elements from Value list Dictionary# Using list comprehension # initializing listtest_list = [4, 6, 3, 10, 5, 3] # printing original listprint("The original list : " + str(test_list)) # initializing dictionary test_dict = {"Gfg" : [5, 3, 6], "is" : [8, 4], "Best" : [10, 11]} # nested loop inside list comprehension to check each key res = [key for ele in test_list for key, val in test_dict.items() if ele in val] # printing result print("The filtered list : " + str(res)) |
The original list : [4, 6, 3, 10, 5, 3] The filtered list : ['is', 'Gfg', 'Gfg', 'Best', 'Gfg', 'Gfg']
Method #2 : Using dictionary comprehension + list comprehension
This is yet another way in which this task can be performed. In this we create inverse dictionary, and map each list value with its key, post that each key is mapped with argument key list elements for matching key value.
Python3
# Python3 code to demonstrate working of # Assigning Key values to list elements from Value list Dictionary# Using dictionary comprehension + list comprehension # initializing listtest_list = [4, 6, 3, 10, 5, 3] # printing original listprint("The original list : " + str(test_list)) # initializing dictionary test_dict = {"Gfg" : [5, 3, 6], "is" : [8, 4], "Best" : [10, 11]} # creating inverse dictionary of elements temp = {j : i for i, k in test_dict.items() for j in k} # creating end result by mapping elementsres = [temp.get(key) for key in test_list] # printing result print("The filtered list : " + str(res)) |
The original list : [4, 6, 3, 10, 5, 3] The filtered list : ['is', 'Gfg', 'Gfg', 'Best', 'Gfg', 'Gfg']
