How To Index and Slice Strings in Python?

The Python string data type is a sequence made up of one or more individual characters that could consist of letters, numbers, whitespace characters, or symbols. As the string is a sequence, it can be accessed in the same ways that other sequence-based data types are, through indexing and slicing.

Indexing

Indexing means referring to an element of an iterable by its position within the iterable. Each of a string’s characters corresponds to an index number and each character can be accessed using its index number. We can access characters in a String in Two ways :

1. Accessing Characters by Positive Index Number
2. Accessing Characters by Negative Index Number

1. Accessing Characters by Positive Index Number: In this type of Indexing, we pass a Positive index(which we want to access) in square brackets. The index number starts from index number 0 (which denotes the first character of a string).

Indexing in Python

Example 1 (Positive Indexing) :

python3

# declaring the string
str = "Geeks for Geeks !"

# accessing the character of str at 0th index
print(str[0])

# accessing the character of str at 6th index
print(str[6])

# accessing the character of str at 10th index
print(str[10])

Output

G
f
G

2. Accessing Characters by Negative Index Number: In this type of Indexing, we pass the Negative index(which we want to access) in square brackets. Here the index number starts from index number -1 (which denotes the last character of a string). Example 2 (Negative Indexing) :

python3

# declaring the string
str = "Geeks for Geeks !"

# accessing the character of str at last index
print(str[-1])

# accessing the character of str at 5th index from the last
print(str[-5])

# accessing the character of str at 10th index from the last
print(str[-10])

Output

!
e
o

Slicing

Slicing in Python is a feature that enables accessing parts of the sequence. In slicing a string, we create a substring, which is essentially a string that exists within another string. We use slicing when we require a part of the string and not the complete string. Syntax :

string[start : end : step]

• start : We provide the starting index.
• end : We provide the end index(this is not included in substring).
• step : It is an optional argument that determines the increment between each index for slicing.

Example 1 :

python3

# declaring the string
str ="Geeks for Geeks !"

# slicing using indexing sequence
print(str[: 3])
print(str[1 : 5 : 2])
print(str[-1 : -12 : -2])

Output

Gee
ek
!seGrf

Example 2 :

python3

# declaring the string
str ="Geeks for Geeks !"

print("Original String :-")
print(str)

# reversing the string using slicing
print("Reverse String :-")
print(str[: : -1])

Output

Original String :-
Geeks for Geeks !
Reverse String :-
! skeeG rof skeeG