Python – Nested Records List from Lists

Last Updated : 14 May, 2020

Sometimes, while working with Python Data, we can have problem in which we have data incoming in different formats. In this, we can receive data as key and value in separate dictionary and we require to make values as list of records with a new key. Lets discuss certain ways in which this task can be performed.

Method #1 : Using zip() + loop
The combination of above functionalities can be used to solve this problem. In this, we perform the pairing using zip and manual intervention of adding key is done in brute way.

# Python3 code to demonstrate working of 
# Nested Records List from Lists
# Using zip() + loop
  
# initializing lists
test_list1 = ['gfg', 'best']
test_list2 = [[1, 2], [3, 4]]
  
# printing original lists
print("The original list 1 is : " + str(test_list1))
print("The original list 2 is : " + str(test_list2))
  
# initializing add_key 
add_key = 'id'
  
# Nested Records List from Lists
# Using zip() + loop
res = dict()
for key, val in zip(test_list1, test_list2):
    res[key]=[{add_key : idx} for idx in val]
  
# printing result 
print("The constructed dictionary is : " + str(res)) 

Output :

The original list 1 is : [‘gfg’, ‘best’]
The original list 2 is : [[1, 2], [3, 4]]
The constructed dictionary is : {‘gfg’: [{‘id’: 1}, {‘id’: 2}], ‘best’: [{‘id’: 3}, {‘id’: 4}]}

Method #2 : Using dictionary comprehension + zip()
This is yet another way to perform this task. This is similar to above method, just a one-liner alternative of above.

# Python3 code to demonstrate working of 
# Nested Records List from Lists
# Using dictionary comprehension + zip()
  
# initializing lists
test_list1 = ['gfg', 'best']
test_list2 = [[1, 2], [3, 4]]
  
# printing original lists
print("The original list 1 is : " + str(test_list1))
print("The original list 2 is : " + str(test_list2))
  
# initializing add_key 
add_key = 'id'
  
# Nested Records List from Lists
# Using dictionary comprehension + zip()
res = {key : [{add_key : idx} for idx in val] 
       for key, val in zip(test_list1, test_list2)}
  
# printing result 
print("The constructed dictionary is : " + str(res)) 

Output :

The original list 1 is : [‘gfg’, ‘best’]
The original list 2 is : [[1, 2], [3, 4]]
The constructed dictionary is : {‘gfg’: [{‘id’: 1}, {‘id’: 2}], ‘best’: [{‘id’: 3}, {‘id’: 4}]}

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Python – Nested Records List from Lists