String Slicing in Python

In this tutorial, you will learn what is string slicing in Python. How many ways you can slice a string and what is it used for. For better understanding, we have lots of examples.

What is String Slicing in Python?

String slicing is a process of extacting a part of a string also called as substring.

It is a very useful feature of Python. While working with strings you will frequently use this feature.

For example, you can extract the first character of a string, last character of a string, first 5 characters of a string, last 5 characters of a string, etc.

"Python" => "p" (first character)
"Python" => "n" (last character)
"Python" => "Pytho" (first 5 characters)
"Python" => "ython" (last 5 characters)

There are many ways to slice a string in Python. We will discuss all of them in this tutorial.

String Slicing Methods

There are two ways to slice a string in Python.

1. Using slice() constructor
2. Using [:] operator

Let's see the syntax of both the methods.

1. Using slice() constructor

The slice() is a constructor in python that returns a slice object. This retured object than later can be used with any string to slice it.

Here is the syntax of slice() constructor.

slice(start, stop)
# or
slice(start, stop, step)

Here:-

• start is the starting index of the slice. It is optional. If not provided, it is considered as 0.
• stop is the ending index of the slice. It is required. The character at this index is not included in the slice.
• step is the step size of the slice. It is optional. If not provided, it is considered as 1.

Let's see some examples.

# using slice() constructor
str1 = "Python is awesome"
str2 = "TutorialsTonight is best to learn Python"

# create object
# slices the string from index 0 to 8
slice1 = slice(0, 9)

# slice the string using slice object
print(str1[slice1]) # Python is
print(str2[slice1]) # Tutorials

Python is
Tutorials

Note: Once you create a slice object, you can use it with any string any number of times to slice it.

Number of arguments:

• If only 1 argument is passed to slice() constructor, it is considered as stop and start is considered as 0.
• If only 2 arguments are passed then, it is considered as start and stop.
• If only 3 arguments are passed then, it is considered as start, stop and step.

# using slice() constructor
str = "Python is awesome"

# only one argument
slice1 = slice(4)
print(str[slice1]) # Pyth

# two arguments
slice2 = slice(4, 9)
print(str[slice2]) # on is

# three arguments
slice3 = slice(0, 16, 2)
print(str[slice3]) # Pto saeo

Pyth
on is
Pto saeo

Using negative indices:

You can also use negative indices to slice a string.

Let's see an example.

# using slice() constructor
str = "Python is awesome"

# using negative indices
slice1 = slice(-7, -1)
print(str[slice1]) # awesom

slice2 = slice(-6, -2)
print(str[slice2]) # weso

awesom
weso

2. Using [:] operator

The [:] operator can also be used to slice a string in Python. Infact it is the most commonly used method to slice a string.

Mainly it is used to slice list so known as list slicing. But it can also be used to slice a string.

Here is the syntax of [:] operator.

str[start]
# or
str[start:stop]
# or
str[start:stop:step]

Here:

• start (optional) is the starting index of the slice. Default value is 0.
• stop (optional) is the ending index of the slice. Default value is the length of the string. The character at this index is not included in the slice.
• step (optional) is the step size of the slice. Default value is 1.

Let's see some examples.

# using [:] operator
str = "Python is awesome"

# slice the string from index 0 to 8
print(str[0:9]) # Python is

Python is

variations of [:] operator

str[start:stop] => slice from 'start' to 'stop-1'
str[start:] => slice from 'start' to the end of the string
str[:stop] => slice from the start of the string to 'stop-1'
str[:] => slice the whole string
str[start:stop:step] => slice from 'start' to 'stop-1' with the step 'step'

Look at the example below.

# using [:] operator
str = "Python is awesome"

# only start given
print(str[8:]) # s awesome

# only stop given
print(str[:8]) # Python i

# start and stop given
print(str[4:9]) # on is

# none given
print(str[:]) # Python is awesome

# start, stop and step given
print(str[0:16:2]) # Pto saeo

s awesome
Python i
on is
Python is awesome
Pto saeo

Using negative indices:

YOu know it that you can access the elements of a string using its index value, but this is also true for negative index. For example, the last character of a string can be accessed using -1 index str[-1].

# using [:] operator
str = "Python is awesome"

# using negative indexing
print(str[-8:]) # awesome
print(str[-8:-1]) # awesom
print(str[-8:-1:2]) # wsm

 awesome
 awesom
 wsm

Reverse string using slicing

To reverse a string in Python, you can use slicing.

For this you need to use the [:] operator and pass the step value as -1.

# reverse a string
str = "Python"
reverse = str[::-1]

print(reverse) # nohtyP

nohtyP

Copy string using slicing

To copy a string in Python, simply take string slicing from 0 to the length of the string and assign it to a new variable.

# copy a string
str = "Python"
copy = str[:]

print(copy) # Python

Python