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How to reverse a string in Python?

Python String is the collection of the Unicode character. Python has numerous functions for string manipulation, but Python string library doesn't support the in-built "reverse()" function. But there are various ways to reverse the string. We are defining the following method to reverse the Python String.

Using for loop
Using while loop
Using the slice operator
Using the reversed() function
Using the recursion

Using for loop

Here, we will reverse the given string using for loop.

     def reverse_string(str):
    str1 = ""   # Declaring empty string to store the reversed string
    for i in str:
        str1 = i + str1
    return str1    # It will return the reverse string to the caller function
   
str = "JavaTpoint"    # Given String     
print("The original string is: ",str)
print("The reverse string is",reverse_string(str)) # Function call

    

Output:

('The original string is: ', 'JavaTpoint')
('The reverse string is', 'tniopTavaJ')

Explanation-

In the above code, we have declared the reverse_string() function and passed the str argument. In the function body, we have declared empty string variable str1 that will hold the reversed string.

Next, the for loop iterated every element of the given string, join each character in the beginning and store in the str1 variable.

After the complete iteration, it returned the reverse order string str1 to the caller function. It printed the result to the screen.

Using while loop

We can also reverse a string using a while loop. Let's understand the following example.

Example -

     # Reverse string
# Using a while loop

str = "JavaTpoint" #  string variable
print ("The original string  is : ",str) 
reverse_String = ""  # Empty String
count = len(str) # Find length of a string and save in count variable
while count > 0: 
    reverse_String += str[ count - 1 ] # save the value of str[count-1] in reverseString
    count = count - 1 # decrement index
print ("The reversed string using a while loop is : ",reverse_String)# reversed string

    

Output:

('The original string  is : ', 'JavaTpoint')
('The reversed string using a while loop is : ', 'tniopTavaJ')

Explanation:

In the above code, we have declared a str variable that holds string value. We initialized a while loop with a value of the string.

In each iteration, the value of str[count - 1] concatenated to the reverse_String and decremented the count value. A while completed its iteration and returned the reverse order string.

Using the slice ([]) operator

We can also reverse the given string using the extended slice operator. Let's understand the following example.

Example -

     #  Reverse a string  
# using  slice syntax 
# reverse(str) Function to reverse a string 
def reverse(str): 
    str = str[::-1] 
    return str 
  
s = "JavaTpoint"
print ("The original string  is : ",s) 
print ("The reversed string using extended slice operator  is : ",reverse(s))

    

Output:

('The original string  is : ', 'JavaTpoint')
('The reversed string(using extended slice syntax) is : ', 'tniopTavaJ')

Explanation:

Generally, a slice operator accepts three parameters - start, stop and step. We provided the no value to start and end index, which indicates the start index is 0 and the end is n-1 by default. The step size is -1; it means the string continues the traverse from the end and goes to the 1 index position.

Using reverse function with join

Python provides the reversed() function to reverse the string. Let's understand the following example.

Example -

     #reverse a string using reversed() 
# Function to reverse a string 
def reverse(str): 
	string = "".join(reversed(str)) # reversed() function inside the join() function
	return string 

s = "JavaTpoint"

print ("The original string is : ",s) 
print ("The reversed string using reversed() is : ",reverse(s) )

    

Output:

('The original string is : ', 'JavaTpoint')
('The reversed string using reversed() is : ', 'tniopTavaJ')

Explanation:

In the function body, we declared the empty string separated by .dot operator. The reversed() string returned the reverse string it joined with the empty string separated using the join() function.

Using recursion()

The string can also be reversed using the recursion. Recursion is a process where function calls itself. Consider the following example.

Example -

     # reverse a string  
# using recursion 
  
def reverse(str): 
    if len(str) == 0: # Checking the lenght of string
        return str 
    else: 
        return reverse(str[1:]) + str[0] 
  
str = "Devansh Sharma" 
print ("The original string  is : ", str)   
print ("The reversed string(using recursion) is : ", reverse(str))

    

Output:

('The original string is : ', 'JavaTpoint')
('The reversed string(using reversed) is : ', 'tniopTavaJ')

Explanation:

In the above code, we have defined a function that accepts the string as an argument.

In the function body, we defined the base condition of recursion, if a length of a string is 0, then the string is returned, and if not then we called the function recursively.

The slice operator slice the string expects the first character and concatenated to the end of the slice string.

Next TopicHow to read CSV file in Python

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