Python Program to display keys with same values in a dictionary List

Given a list with all dictionary elements, the task is to write a Python program to extract keys having similar values across all dictionaries.

Examples:

Input : test_list = [{"Gfg": 5, "is" : 8, "best" : 0}, {"Gfg": 5, "is" : 1, "best" : 0}, {"Gfg": 5, "is" : 0, "best" : 0}] 
Output : ['Gfg', 'best'] 
Explanation : All Gfg values are 5 and best has 0 as all its values in all dictionaries.

Input : test_list = [{"Gfg": 5, "is" : 8, "best" : 1}, {"Gfg": 5, "is" : 1, "best" : 0}, {"Gfg": 5, "is" : 0, "best" : 0}] 
Output : ['Gfg'] 
Explanation : All Gfg values are 5. 

Method 1 : Using keys() and loop

In this, we iterate through all the elements in the list using loop and extract keys using keys(). For each key, each dictionary's key is compared, if found similar, key is added to result.

Output:

The original list is : [{'Gfg': 5, 'is': 8, 'best': 0}, {'Gfg': 5, 'is': 1, 'best': 0}, {'Gfg': 5, 'is': 0, 'best': 0}]

Similar values keys : ['Gfg', 'best']

Time Complexity: O(n*n)
Auxiliary Space: O(n)

Method 2 : Using all(), loop and keys()

In this, inner loop is avoided and replaced by all() which checks for all the keys having similar values and then the key is extracted.

Output:

The original list is : [{'Gfg': 5, 'is': 8, 'best': 0}, {'Gfg': 5, 'is': 1, 'best': 0}, {'Gfg': 5, 'is': 0, 'best': 0}]

Similar values keys : ['Gfg', 'best']

Time Complexity: O(n*n)
Auxiliary Space: O(n)

Method 3:  Use the set intersection method. 

Step-by-step approach:

• Initialize an empty set intersection_set to store the keys with similar values.
• Iterate through the keys of the first dictionary in the test_list using a for loop.
• For each key, check if the values of that key in all the dictionaries in the test_list are the same using a list comprehension and the set() function.
• If the length of the resulting set is 1, then add the key to the intersection_set.
• Print the intersection_set.

Below is the implementation of the above approach:

The original list is : [{'Gfg': 5, 'is': 8, 'best': 0}, {'Gfg': 5, 'is': 1, 'best': 0}, {'Gfg': 5, 'is': 0, 'best': 0}]
Similar values keys : ['Gfg', 'best']

Time complexity: O(N*M) where N is the number of dictionaries in the test_list and M is the number of keys in the first dictionary. 
Auxiliary space: O(M) to store the intersection_set.

Method 4:  Using reduce():
 

Algorithm:

1. Import the reduce function from functools module
2. Initialize the test_list with dictionaries containing key-value pairs
3. Get the keys of the first dictionary from the test_list
4. Use the reduce function to iterate over the keys and check if all the values in the corresponding key in all the dictionaries are equal to the value of that key in the first dictionary. If yes, add the key to the result list.
5. Print the result list.

The original list is : [{'Gfg': 5, 'is': 8, 'best': 0}, {'Gfg': 5, 'is': 1, 'best': 0}, {'Gfg': 5, 'is': 0, 'best': 0}]
Similar values keys : ['Gfg', 'best']

Time Complexity: O(n*m), where n is the number of keys and m is the number of dictionaries in the test_list. This is because we need to iterate over all the keys and dictionaries to check for similar values.

Space Complexity: O(k), where k is the number of keys in the test_list. This is because we are only storing the result list, which can have a maximum of k elements.