In this post, let us discuss slicing in python with examples.
How Indexing works ?
For your reminder, Indexing starts from zero.
In the below example, a[0] & a[1] help us to get the element present in the zeroth and first index position
Program
print("creating a new list")
a=[9,8,7,6,5,4,3,2,1]
print("printing the elements of the list")
print(a)
print("printing the first element")
print(a[0])
print("printing the second element")
print(a[1])Output
creating a new list
printing the elements of the list
[9, 8, 7, 6, 5, 4, 3, 2, 1]
printing the first element
9
printing the second element
8What is Slicing ?
Slicing in python helps us in getting the specific range of elements based on their position from the collection.
Here comes the syntax of slicing which lists the range from index position one to two. It neglects the element present in the third index.
Below is the official document
https://docs.python.org/2.3/whatsnew/section-slices.html
Slicing in Python
Program
a=[9,8,7,6,5,4,3,2,1]
print("printing the first 3 elements of a list")
print(a[0:3])
print("other way to print first 3 elements of a list")
print(a[:3])Output
printing the first 3 elements of a list
[9, 8, 7]
other way to print first 3 elements of a list
[9, 8, 7]Positive and Negative indexing in slicing
There are two types of indexing available :
1) Positive Indexing
2) Negative Indexing
Positive Indexing
Program
a=[9,8,7,6,5,4,3,2,1]
print("printing second and third element in a list")
print(a[1:3])Output
printing second and third element in a list
[8, 7]Negative indexing
Program
a=[9,8,7,6,5,4,3,2,1]
print("printing the last element")
print(a[-1])
print("printing last three elements in a list")
print(a[-3:])
print("printing from second element till second last element")
print(a[1:-1])Output
printing the last element
1
printing last three elements in a list
[3, 2, 1]
printing from second element till second last element
[8, 7, 6, 5, 4, 3]Interview Q&A
How to reverse the elements present in a list?
Program
a=[9,8,7,6,5,4,3,2,1]
print("Reversing the elements")
print(a[::-1])Output
Reversing the elements
[1, 2, 3, 4, 5, 6, 7, 8, 9]