String Slicing in Python

Python slicing is about obtaining a sub-string from the given string by slicing it respectively from start to end. 

How String slicing in Python works

For understanding slicing we will use different methods, here we will cover 2 methods of string slicing, one using the in-build slice() method and another using the [:] array slice. String slicing in Python is about obtaining a sub-string from the given string by slicing it respectively from start to end. 

Python slicing can be done in two ways:

• Using a slice() method
• Using the array slicing  [:: ] method

Index tracker for positive and negative index: String indexing and slicing in python. Here, the Negative comes into consideration when tracking the string in reverse. 

Method 1: Using the slice() method

The slice() constructor creates a slice object representing the set of indices specified by range(start, stop, step).

Syntax:

• slice(stop)
• slice(start, stop, step)

Parameters: start: Starting index where the slicing of object starts. stop: Ending index where the slicing of object stops. step: It is an optional argument that determines the increment between each index for slicing. Return Type: Returns a sliced object containing elements in the given range only. 

Example:

Python3

# Python program to demonstrate
# string slicing

# String slicing
String = 'ASTRING'

# Using slice constructor
s1 = slice(3)
s2 = slice(1, 5, 2)
s3 = slice(-1, -12, -2)

print("String slicing")
print(String[s1])
print(String[s2])
print(String[s3])

Output:

String slicing
AST
SR
GITA

Method 2: Using the List/array slicing  [ :: ]  method

In Python, indexing syntax can be used as a substitute for the slice object. This is an easy and convenient way to slice a string using list slicing and Array slicing both syntax-wise and execution-wise. A start, end, and step have the same mechanism as the slice() constructor. 

Below we will see string slicing in Python with examples.

Syntax

arr[start:stop]         # items start through stop-1
arr[start:]             # items start through the rest of the array
arr[:stop]              # items from the beginning through stop-1
arr[:]                  # a copy of the whole array
arr[start:stop:step]    # start through not past stop, by step

Example 1:

In this example, we will see slicing in python list the index start from 0 indexes and ending with a 2 index(stops at 3-1=2 ).

Python3

# Python program to demonstrate
# string slicing

# String slicing
String = 'GEEKSFORGEEKS'

# Using indexing sequence
print(String[:3])

Output:

GEE

Example 2:

In this example, we will see the example of starting from 1 index and ending with a 5 index(stops at 3-1=2 ), and the skipping step is 2. It is a good example of Python slicing string by character.

Python3

# Python program to demonstrate
# string slicing

# String slicing
String = 'GEEKSFORGEEKS'

# Using indexing sequence
print(String[1:5:2])

Output:

EK

Example 3:

In this example, we will see the example of starting from -1 indexes and ending with a -12 index(stops at 3-1=2 )and the skipping step is -2.

Python3

# Python program to demonstrate
# string slicing

# String slicing
String = 'GEEKSFORGEEKS'

# Using indexing sequence
print(String[-1:-12:-2])

Output:

SEGOSE

Example 4:

In this example, the whole string is printed in reverse order.

Python3

# Python program to demonstrate
# string slicing

# String slicing
String = 'GEEKSFORGEEKS'

# Prints string in reverse
print(String[::-1])

Output:

SKEEGROFSKEEG

Note: To know more about strings click here.

Using islice()
The islice() is a built-in function defined in itertools module. It is used to get an iterator which is an index-based slicing of any iterable. It works like a standard slice but returns an iterator.

Syntax:

itertools.islice(iterable, start, stop[, step])
Parameters: iterable: Any iterable sequence like list, string, tuple etc. start: The start index from where the slicing of iterable starts. stop: The end index from where the slicing of iterable ends. step: An optional argument. It specifies the gap between each index for slicing. Return Type: Return an iterator from the given iterable sequence.

Example:

Python3

# Python program to demonstrate
# islice()

import itertools

# Using islice()
String = 'GEEKSFORGEEKS'

# prints characters from 3 to 7 skipping one character.
print(''.join(itertools.islice(String, 3, 7)))
#This code is contributed by Edula Vinay Kumar Reddy

Output

KSFO