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Python – Extract Kth index elements from Dictionary Value list
  • Last Updated : 01 Aug, 2020

Given a dictionary with list as values, extract all the Kth index elements.

Input : {“Gfg” : [4, 7, 5], “Best” : [8, 6, 7], “is” : [9, 3, 8]}, K = 2
Output : [5, 7, 8]
Explanation : The 2nd index elements are 5, 7 and 8 respectively in different keys.

Input : {“Gfg” : [4, 7, 5], “Best” : [8, 6, 7], “is” : [9, 3, 8]}, K = 0
Output : [4, 8, 9]
Explanation : The 0th index elements are 4, 8 and 9 respectively in different keys.

Method #1 : Using list comprehension + values()

The combination of above functionalities can be used to solve this problem. In this, the values are extracted using values() and list comprehension is used to construct new list.



Python3




# Python3 code to demonstrate working of 
# Extract Kth index elements from Dictionary Value list
# Using list comprehension + values()
  
# initializing dictionary
test_dict = {"Gfg" : [4, 7, 5], "Best" : [8, 6, 7], "is" : [9, 3, 8]}
  
# printing original dictionary
print("The original dictionary is : " + str(test_dict))
  
# initializing K 
K = 1
  
# one liner, values() getting all value according to keys
res = [sub[K] for sub in test_dict.values()]
  
# printing result 
print("The extracted values : " + str(res)) 
Output
The original dictionary is : {'Gfg': [4, 7, 5], 'Best': [8, 6, 7], 'is': [9, 3, 8]}
The extracted values : [7, 6, 3]

Method #2 : Using map() + itemgetter()

The combination of above functionalities can be used to solve this problem. In this, we use map() to extend logic of getting values of particular key, and itemgetter is used for extracting particular index.

Python3




# Python3 code to demonstrate working of 
# Extract Kth index elements from Dictionary Value list
# Using map() + itemgetter()
from operator import itemgetter
  
# initializing dictionary
test_dict = {"Gfg" : [4, 7, 5], "Best" : [8, 6, 7], "is" : [9, 3, 8]}
  
# printing original dictionary
print("The original dictionary is : " + str(test_dict))
  
# initializing K 
K = 1
  
# map and itemgetter() extracting result 
# list() used to convert result from map() to list format
res = list(map(itemgetter(K), test_dict.values()))
  
# printing result 
print("The extracted values : " + str(res)) 
Output
The original dictionary is : {'Gfg': [4, 7, 5], 'Best': [8, 6, 7], 'is': [9, 3, 8]}
The extracted values : [7, 6, 3]

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