Python | K elements Slicing

We often come to the situations in which we need to extract initial K elements of list. This particular problem occurs when we need to optimize memory. This has its application in the day-day programming when sometimes we require to get all the lists of similar size. Let’s discuss certain ways in which this task can be performed.

Method #1 : Using len() + list slicing
List slicing can perform this particular task in which we just slice the first K elements to be in the list and hence removing the remaining elements, freeing memory.

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# Python code to demonstrate 
# K elements Slicing
# using len() + list slicing
  
# initializing list 
test_list = [1, 4, 6, 3, 5, 8]
  
# printing original list
print ("The original list is : " + str(test_list))
  
# initializing K 
K = 4
  
# using len() + list slicing
# K elements Slicing
res = test_list[: K]
  
# printing result 
print ("The K sliced List : " + str(res))

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Output :



The original list is : [1, 4, 6, 3, 5, 8]
The K sliced List : [1, 4, 6, 3]

 

Method #2 : Using Negative list slicing
We can perform this particular task using the negative list slicing in which we start removing the elements from the last index of the list and hence remove all the N – K elements from the last. We remove None if 0 elements are asked to be removed.

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# Python code to demonstrate 
# K elements Slicing
# using negative list slicing
  
# initializing list 
test_list = [1, 4, 6, 3, 5, 8]
  
# printing original list
print ("The original list is : " + str(test_list))
  
# initializing K 
K = 4
  
# using negative list slicing
# K elements Slicing
res = test_list[ : -(len(test_list) - K)]
  
# printing result 
print ("The K sliced List : " + str(res))

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Output :

The original list is : [1, 4, 6, 3, 5, 8]
The K sliced List : [1, 4, 6, 3]


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