Python – Mapping key values to Dictionary

Difficulty Level : Hard
Last Updated : 22 Apr, 2020

Sometimes, while working with Python records, we can have a problem in which we need to extract key’s value as the dictionary values required. This can have application in domains in which we require to reduce the data storage and in web development domain. Lets discuss certain ways in which this task can be performed.

Method #1 : Using dictionary comprehension
This is one of the way in which we can solve this problem. In this, we iterate the list keys and construct dictionary of required key-value pairs using dictionary comprehension.

# Python3 code to demonstrate working of 
# Mapping key values to Dictionary
# Using dictionary comprehension
  
# initializing list
test_list = [{'name' : 'Manjeet', 'age' : 23}, 
             {'name' : 'Akshat',  'age' : 22},
             {'name' : 'Nikhil', 'age' : 21}]
  
# printing original list
print("The original list is : " + str(test_list))
  
# Mapping key values to Dictionary
# Using dictionary comprehension
res = {sub['name'] : sub['age'] for sub in test_list}
  
# printing result 
print("The flattened dictionary is : " + str(dict(res))) 

Output :

The original list is : [{‘age’: 23, ‘name’: ‘Manjeet’}, {‘age’: 22, ‘name’: ‘Akshat’}, {‘age’: 21, ‘name’: ‘Nikhil’}]
The flattened dictionary is : {‘Manjeet’: 23, ‘Akshat’: 22, ‘Nikhil’: 21}

Method #2 : Using dict() + values()
The combination of above functions can also be used to solve this problem. In this, we perform conversion to dictionary using dict() and extract dictionary values using values().

# Python3 code to demonstrate working of 
# Mapping key values to Dictionary
# Using dict() + values()
  
# initializing list
test_list = [{'name' : 'Manjeet', 'age' : 23}, 
             {'name' : 'Akshat',  'age' : 22},
             {'name' : 'Nikhil', 'age' : 21}]
  
# printing original list
print("The original list is : " + str(test_list))
  
# Mapping key values to Dictionary
# Using dict() + values()
res = dict(sub.values() for sub in test_list)
  
# printing result 
print("The flattened dictionary is : " + str(dict(res))) 

Output :

The original list is : [{‘age’: 23, ‘name’: ‘Manjeet’}, {‘age’: 22, ‘name’: ‘Akshat’}, {‘age’: 21, ‘name’: ‘Nikhil’}]
The flattened dictionary is : {‘Manjeet’: 23, ‘Akshat’: 22, ‘Nikhil’: 21}

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Python – Mapping key values to Dictionary