Python – Assign Reversed Values in Dictionary
Given a dictionary, assign each key, values after reverting the values of dictionary.
Input : {1 : 4, 2 : 5, 3 : 6} Output : {1 : 6, 2 : 5, 3 : 4} Explanation : Value order changed, 4, 5, 6 to 6, 5, 4. Input : {1 : 5, 2 : 5, 3 : 5} Output : {1 : 5, 2 : 5, 3 : 5} Explanation : Same values, no visible change.
Method #1 : Using values() + loop + reversed()
This is one of the ways in which this task can be performed. In this, we reverse all the values in dictionary using reversed() and reassign to keys.
Python3
# Python3 code to demonstrate working of # Assign Reversed Values in Dictionary# Using reversed() + loop + values()# initializing dictionarytest_dict = {1 : "Gfg", 2 : "is", 3 : "Best"}# printing original dictionaryprint("The original dictionary is : " + str(test_dict))# extract values using values()new_val = list(reversed(list(test_dict.values())))# reassign new valuesres = dict()cnt = 0for key in test_dict: res[key] = new_val[cnt] cnt += 1# printing result print("Reassigned reverse values : " + str(res)) |
The original dictionary is : {1: 'Gfg', 2: 'is', 3: 'Best'}
Reassigned reverse values : {1: 'Best', 2: 'is', 3: 'Gfg'}
Time complexity: O(n), where n is the number of key-value pairs in the dictionary.
Auxiliary space: O(n), to store the keys and values in dictionary.
Method #2 : Using dictionary comprehension + reversed() + values()
The combination of above functions can be used to solve this problem. In this, we perform the task of remaking reversed dictionary using dictionary comprehension recipe for one-liner solution.
Python3
# Python3 code to demonstrate working of # Assign Reversed Values in Dictionary# Using dictionary comprehension + reversed() + values()# initializing dictionarytest_dict = {1 : "Gfg", 2 : "is", 3 : "Best"}# printing original dictionaryprint("The original dictionary is : " + str(test_dict))# extract values using values()new_val = list(reversed(list(test_dict.values())))# one-liner dictionary comprehension approach# enumerate for counterres = {key : new_val[idx] for idx, key in enumerate(list(test_dict.keys()))}# printing result print("Reassigned reverse values : " + str(res)) |
The original dictionary is : {1: 'Gfg', 2: 'is', 3: 'Best'}
Reassigned reverse values : {1: 'Best', 2: 'is', 3: 'Gfg'}
Method 3: Using the zip() function and a for loop:
- Initialize the input dictionary.
- Extract the keys and values from the dictionary using the keys() and values() methods respectively, and store them in separate lists.
- Reverse the order of the values list using the reversed() function and convert it to a list using the list() function.
- Use the zip() function to create an iterable of tuples, where each tuple contains a key-value pair from the input dictionary.
- Use a for loop to iterate through the iterable of tuples and assign each key in the new dictionary to the corresponding reversed value from the values list.
- Return the new dictionary with reversed values.
Python3
# Python3 code to demonstrate working of # Assign Reversed Values in Dictionary# Using zip() + reversed()# initializing dictionarytest_dict = {1 : "Gfg", 2 : "is", 3 : "Best"}# printing original dictionaryprint("The original dictionary is : " + str(test_dict))# extract keys and values using keys() and values()keys = list(test_dict.keys())values = list(reversed(list(test_dict.values())))# using zip() to create a dictionaryres = {}for key, value in zip(keys, values): res[key] = value# printing result print("Reassigned reverse values : " + str(res)) |
The original dictionary is : {1: 'Gfg', 2: 'is', 3: 'Best'}
Reassigned reverse values : {1: 'Best', 2: 'is', 3: 'Gfg'}
Time complexity: O(n), where n is the number of key-value pairs in the dictionary.
Auxiliary space: O(n), to store the keys and values in lists.
