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Python | Column deletion from list of lists

  • Last Updated : 26 Feb, 2019

The problem of removing a row from a list is quite simple and we just need to pop a list out of list of lists. But there can be a utility where we need to delete a column i.e particular index element of each of the list. This is problem that can occur if we store any database data into containers. Let’s discuss certain ways in which this can be performed.

Method #1 : Using del + loop
In this strategy, we just delete the column element one by one using a loop to iterate the row number at each of the iteration.




# Python3 code to demonstrate 
# deleting columns of list of lists
# using del + loop
  
# initializing list 
test_list = [[4, 5, 6, 8],
             [2, 7, 10, 9],
             [12, 16, 18, 20]]
  
# printing original list
print ("The original list is : " + str(test_list))
  
# using del + loop
# deleting column element of row
for j in test_list:
    del j[1]
  
# printing result 
print ("The modified mesh after column deletion : " +  str(test_list))

Output :

The original list is : [[4, 5, 6, 8], [2, 7, 10, 9], [12, 16, 18, 20]]
The modified mesh after column deletion : [[4, 6, 8], [2, 10, 9], [12, 18, 20]]

 



Method #2 : Using pop() + list comprehension
We can do this particular task in an easier and shorter way using the list comprehension technique and using the pop function which can be used to remove the list element.




# Python3 code to demonstrate 
# deleting columns of list of lists
# using pop() + list comprehension
  
# initializing list 
test_list = [[4, 5, 6, 8],
             [2, 7, 10, 9],
             [12, 16, 18, 20]]
  
# printing original list
print ("The original list is : " + str(test_list))
  
# using pop() + list comprehension
# deleting column element of row
[j.pop(1) for j in test_list]
  
# printing result 
print ("The modified mesh after column deletion : " +  str(test_list))

Output :

The original list is : [[4, 5, 6, 8], [2, 7, 10, 9], [12, 16, 18, 20]]
The modified mesh after column deletion : [[4, 6, 8], [2, 10, 9], [12, 18, 20]]

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