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Python – Extract Unique value key pairs
  • Last Updated : 26 May, 2020

Sometimes, while working on Python dictionaries, we can have a problem in which we need to perform the extraction of selected pairs of keys from dictionary list, that too unique. This kind of problem can have application in many domains including day-day programming. Let’s discuss certain ways in which this task can be performed.

Input : test_list = [{‘gfg’ : 5, ‘best’ : 12}, {‘gfg’ : 5, ‘best’ : 12}, ]
Output : {(5, 12)}

Input : test_list = [{‘gfg’ : 5, ‘is’: 5, ‘best’ : 12}]
Output : {(5, 12)}

Method #1 : Using list comprehension
This problem can be solved using above functionality. In this, we perform the match, using conditionals and “in” operator. The whole logic compiled using list comprehension.




# Python3 code to demonstrate working of 
# Extract Unique value key pairs
# Using list comprehension
  
# initializing list
test_list = [{'gfg' : 5, 'is' : 8, 'best' : 12}, 
             {'gfg' : 5, 'is' : 12, 'best' : 12},
             {'gfg' : 20, 'is' : 17, 'best' : 12}]
  
# printing original list
print("The original list is : " + str(test_list))
  
# initializing required keys
req_key1 = 'gfg'
req_key2 = 'best'
  
# Extract Unique value key pairs
# Using list comprehension
res =  {tuple(sub[idx] for idx in [req_key1, req_key2]) for sub in test_list}
  
# printing result 
print("The required values : " + str(res)) 
Output :



The original list is : [{‘gfg’: 5, ‘is’: 8, ‘best’: 12}, {‘gfg’: 5, ‘is’: 12, ‘best’: 12}, {‘gfg’: 20, ‘is’: 17, ‘best’: 12}]
The required values : {(5, 12), (20, 12)}

 

Method #2 : Using map() + zip() + itemgetter()
The combination of above functionalities can be used to perform this task. In this, we use itemgetter to extract the values, zip() is used to combine values, and map() is used to convert the combined result to set.




# Python3 code to demonstrate working of 
# Extract Unique value key pairs
# Using map() + zip() + itemgetter()
from operator import itemgetter
  
# initializing list
test_list = [{'gfg' : 5, 'is' : 8, 'best' : 12}, 
             {'gfg' : 5, 'is' : 12, 'best' : 12},
             {'gfg' : 15, 'is' : 17, 'best' : 21}]
  
# printing original list
print("The original list is : " + str(test_list))
  
# initializing required keys
req_key1 = 'gfg'
req_key2 = 'best'
  
# Extract Unique value key pairs
# Using map() + zip() + itemgetter()
temp = zip(*map(itemgetter(req_key1, req_key2), test_list))
res = list(map(set, temp))
  
# printing result 
print("The required values : " + str(res)) 
Output :

The original list is : [{‘gfg’: 5, ‘is’: 8, ‘best’: 12}, {‘gfg’: 5, ‘is’: 12, ‘best’: 12}, {‘gfg’: 15, ‘is’: 17, ‘best’: 21}]
The required values : [{5, 15}, {12, 21}]

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