Python – Convert Key-Value list Dictionary to List of Lists

Last Updated : 22 Apr, 2020

Sometimes, while working with Python dictionary, we can have a problem in which we need to perform the flattening a key value pair of dictionary to a list and convert to lists of list. This can have applications in domains in which we have data. Lets discuss certain ways in which this task can be performed.

Method #1 : Using loop + items()
This brute force way in which we can perform this task. In this, we loop through all the pairs and extract list value elements using items() and render in a new list.

# Python3 code to demonstrate working of 
# Convert Key-Value list Dictionary to Lists of List
# Using loop + items()
  
# initializing Dictionary
test_dict = {'gfg' : [1, 3, 4], 'is' : [7, 6], 'best' : [4, 5]}
  
# printing original dictionary
print("The original dictionary is : " + str(test_dict))
  
# Convert Key-Value list Dictionary to Lists of List
# Using loop + items()
res = []
for key, val in test_dict.items():
    res.append([key] + val)
  
# printing result 
print("The converted list is : " + str(res)) 

Output :

The original dictionary is : {‘gfg’: [1, 3, 4], ‘is’: [7, 6], ‘best’: [4, 5]}
The converted list is : [[‘gfg’, 1, 3, 4], [‘is’, 7, 6], [‘best’, 4, 5]]

Method #2 : Using list comprehension
This task can also be performed using list comprehension. In this, we perform the task similar to above method just in one-liner shorter way.

# Python3 code to demonstrate working of 
# Convert Key-Value list Dictionary to Lists of List
# Using list comprehension
  
# initializing Dictionary
test_dict = {'gfg' : [1, 3, 4], 'is' : [7, 6], 'best' : [4, 5]}
  
# printing original dictionary
print("The original dictionary is : " + str(test_dict))
  
# Convert Key-Value list Dictionary to Lists of List
# Using list comprehension
res = [[key] + val for key, val in test_dict.items()]
  
# printing result 
print("The converted list is : " + str(res)) 

Output :

The original dictionary is : {‘gfg’: [1, 3, 4], ‘is’: [7, 6], ‘best’: [4, 5]}
The converted list is : [[‘gfg’, 1, 3, 4], [‘is’, 7, 6], [‘best’, 4, 5]]

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Python – Convert Key-Value list Dictionary to List of Lists