We will develop a Python program to reverse a string. In this article, we are using the for loop, while loop, reversed() function, slice operator, and recursion methods to reverse a string in python.
Example of reverse string:-
String: Know Program
Reverse String: margorP wonK
Reverse a String in Python using For Loop
We will take a string while declaring the variables. Then, the for loop iterates every element of the given string, joining each character in the beginning so as to obtain the reversed string. Finally, the result will be displayed on the screen.
The len() function returns the number of items in an object. When the object is a string, the len() function returns the number of characters in the string. The range() method returns an immutable sequence of numbers between the given start integer to the stop integer.
Program description:- Write a python program to reverse a string from user input
# Python program to reverse a string using for loop
# take inputs
string = input('Enter the string: ')
# calculate reverse of string
reverse = ''
for i in range(len(string), 0, -1):
reverse += string[i-1]
# print reverse of string
print('The reverse string is', reverse)
Output for the input values test-case-1:-
Enter the string: Know Program
The reverse string is margorP wonK
Output for the input values test-case-2:-
Enter the string: reverse
The reverse string is esrever
Output for the input values test-case-3:-
Enter the string: For loop
The reverse string is pool roF
Function to Reverse a String in Python
We can also take the help of a function to reverse a string in python. A function is a block of code that performs a specific task.
# Python program to reverse a string using function
def findReverse(string): #user-defined function
# find reverse of string
reverse = ''
for i in range(len(string), 0, -1):
reverse += string[i-1]
return reverse
# take inputs
string = input('Enter the string: ')
# calling function and display result
reverse = findReverse(string)
print('The reverse string is', reverse)Output for the input values test-case-1:-
Enter the string: function
The reverse string is noitcnuf
Output for the input values test-case-2:-
Enter the string: Python
The reverse string is nohtyP
Program to Reverse a String in Python using While Loop
In the previous program, we used the for loop but in this program, we use the while loop to reverse a string. We initialized a while loop with a value of the string.
Program description:- Write a program to reverse a string in Python
# Python program to reverse a string using while loop
def findReverse(string): #user-defined function
#find reverse of string
i = string
reverse = ''
while(len(i) > 0):
if(len(i) > 0):
a = i[-1]
i = i[:-1]
reverse += a
return reverse
# take inputs
string = input('Enter the string: ')
# calling function and display result
reverse = findReverse(string)
print('The reverse string is', reverse)
Output for the input values test-case-1:-
Enter the string: while loop
The reverse string is pool elihw
Output for the input values test-case-2:-
Enter the string: reverse of string
The reverse string is gnirts fo esrever
Python Program to Reverse a String using Slicing
The slice() function returns a slice object. A slice object is used to specify how to slice a sequence. You can specify where to start the slicing, and where to end.
# Python program to reverse a string using slicing
def findReverse(string): #user-defined function
# find reverse of string
reverse = string[::-1]
return reverse
# take inputs
string = input('Enter the string: ')
# calling function and display result
reverse = findReverse(string)
print('The reverse string is', reverse)
Output:-
Enter the string: slicing
The reverse string is gnicils
Print Reverse String in Python using inbuilt Function
We are using a predefined function join(reversed()). Python reversed() method returns an iterator that accesses the given sequence in the reverse order.
Program description:- Write a python function to reverse a string
# Python program to reverse a string using inbuilt function
def reverse(string): #user-defined functon
# find reverse using buit-in functions
reverse = ''.join(reversed(string))
return reverse
# take inputs
string = input('Enter the string: ')
# calling function and display result
print('The reverse string is', reverse(string))
Output:-
Enter the string: inbuilt function
The reverse string is noitcnuf tliubni
Reverse String Recursion in Python
We can use the recursion technique to reverse a string in Python. A technique of defining the method/function that contains a call to itself is called recursion. The recursive function/method allows us to divide the complex problem into identical single simple cases that can be handled easily. This is also a well-known computer programming technique: divide and conquer.
# Python program to reverse a string using recursion
def findReverse(string): #user-defined function
# find reverse of string
if len(string) == 0:
return string
else:
return findReverse(string[1:]) + string[0]
# take inputs
string = input('Enter the string: ')
# calling function and display result
reverse = findReverse(string)
print('The reverse string is', reverse)
Output:-
Enter the string: recursion
The reverse string is noisrucer
Q1) Write a python program to reverse a string sample string 1234abcd.
# Python program to reverse a string
def findReverse(string): #user-defined function
# find reverse of string
reverse = ''
for i in range(len(string), 0, -1):
reverse += string[i-1]
return reverse
# take inputs
string = '1234abcd'
# calling function and display result
print('The reverse string is', findReverse(string))
Output:-
The reverse string is dcba4321
