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Python | Adding value to sublists
  • Last Updated : 08 Apr, 2019

Sometimes, we just have to manipulate a list of lists by appending a similar value to all the sublists. Using a loop for achieving this particular task can be an option but sometimes leads to sacrifice the readability of code. It is always wanted to have a oneliner to perform this particular task. Let’s discuss certain ways in which this can be done.

Method #1 : Using list comprehension
List comprehension can be used to perform this particular task using a similar looping construct but in just a single line. This increases code readability.

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# Python3 code to demonstrate 
# appending single value 
# using list comprehension 
  
# initializing list of lists
test_list = [[1, 3], [3, 4], [6, 5], [4, 5]]
  
# printing original list 
print("The original list : " +  str(test_list))
  
# declaring element to be inserted
K = "GFG"
  
# using list comprehension 
# appending single value
res = [[i, j, K ] for i, j in test_list]
  
# printing result 
print("The list after adding element :  " + str(res))

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Output :

The original list : [[1, 3], [3, 4], [6, 5], [4, 5]]
The list after adding element : [[1, 3, ‘GFG’], [3, 4, ‘GFG’], [6, 5, ‘GFG’], [4, 5, ‘GFG’]]

 



Method #2 : Using list comprehension + "+" operator
This method is quite similar to the above method, but the difference is that plus operator is used to add the new element to each sublist.

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# Python3 code to demonstrate 
# appending single value 
# using list comprehension + "+" operator
  
# initializing list of lists
test_list = [[1, 3], [3, 4], [6, 5], [4, 5]]
  
# printing original list 
print("The original list : " +  str(test_list))
  
# declaring element to be inserted
K = "GFG"
  
# using list comprehension + "+" operator
# appending single value
res = [sub + [K] for sub in test_list]
  
# printing result 
print("The list after adding element :  " + str(res))

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Output :

The original list : [[1, 3], [3, 4], [6, 5], [4, 5]]
The list after adding element : [[1, 3, ‘GFG’], [3, 4, ‘GFG’], [6, 5, ‘GFG’], [4, 5, ‘GFG’]]

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