Python - Extract Equal Pair Dictionary

Python – Extract Equal Pair Dictionary

Last Updated : 08 May, 2020

Sometimes, while working with Python dictionary, we can have problem in which we need to create a new dictionary of the existing dictionary having tuple as key. We desire to create singlton key dictionary with keys only where both elements of pair are equal. This can have application in many domains. Let’s discuss certain ways in which this task can be performed.

Method #1 : Using loop
This is brute way in which this task can be performed. In this, we iterate for each element of tuple dictionary and compare for equality to create new dictionary.

# Python3 code to demonstrate working of 
# Extract Equal Pair Dictionary 
# Using loop
  
# initializing dictionary
test_dict = { (1, 1) : 4, (2, 3) : 6, (3, 3) : 7, (5, 2) : 10, (2, 2) : 11}
  
# printing original dictionary
print("The original dictionary is : " + str(test_dict))
  
# Extract Equal Pair Dictionary 
# Using loops
res = dict()
for key, val in test_dict.items():
    if key[0] == key[1]:
        res[key[0]] = val
  
# printing result 
print("The dictionary after equality testing : " + str(res)) 

Output :

The original dictionary is : {(5, 2): 10, (2, 2): 11, (2, 3): 6, (1, 1): 4, (3, 3): 7}
The dictionary after equality testing : {1: 4, 2: 11, 3: 7}

Method #2 : Using dictionary comprehension
This is yet another way in which this task can be performed. In this we use dictionary comprehension instead of loop to provide shorthand.

# Python3 code to demonstrate working of 
# Extract Equal Pair Dictionary 
# Using dictionary comprehension
  
# initializing dictionary
test_dict = { (1, 1) : 4, (2, 3) : 6, (3, 3) : 7, (5, 2) : 10, (2, 2) : 11}
  
# printing original dictionary
print("The original dictionary is : " + str(test_dict))
  
# Extract Equal Pair Dictionary 
# Using dictionary comprehension
res = {idx[0] : j for idx, j in test_dict.items() if idx[0] == idx[1]}
  
# printing result 
print("The dictionary after equality testing : " + str(res)) 

Output :

The original dictionary is : {(5, 2): 10, (2, 2): 11, (2, 3): 6, (1, 1): 4, (3, 3): 7}
The dictionary after equality testing : {1: 4, 2: 11, 3: 7}

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