Python Reverse String

Strings are basically sequence of characters. Python doesn’t support in-built string functions such as reverse() to reverse a string.

The following are the ways to reverse a string in Python:

By using a for loop
By using a while loop
By using a Slicing
By using join() method
By using Recursion
By using List reverse() method
By using stack

Method 1: Reverse a string using for loop

def rev_string_loop(s):
    res = ''
    for x in s:
        res = x + res
    return res

str = 'STRING'


print('Reversed String =', rev_string_loop(str))

Output:

Reversed String = GNIRTS

Method 2: Reverse a string using while loop

def rev_string_loop(x):
    res = ''
    length = len(x) - 1
    while length >= 0:
        res = res + x[length]
        length = length - 1
    return res

str = 'STRING'

print('Reversed String =', rev_string_loop(str))

Output:

Reversed String = GNIRTS

Method 3: Reverse a string using Slicing

input="STRING" 
length=len(input) 
res=input[length::-1] 
print (res)

Output:

GNIRTS

Method 4: Reverse a string using join() method

input = 'STRING' 
result=''.join(reversed(input)) 
print(result)

Output:

GNIRTS

Method 5: Reverse a string using Recursion

def rev_string(x): 
    if len(x) == 0: 
        return x 
    else: 
        return rev_string(x[1:]) + x[0] 
  
x = "STRING"
  
print ("Original string: ") 
print (x) 
  
print ("Reversed string: ") 
print (rev_string(x))

Output:

Original string:
STRING
Reversed string:
GNIRTS

Method 6: Reverse a string using List reverse() method

input_list = [1, 2, 3, 4, 5]


input_list.reverse()


print(input_list)

Output:

[5, 4, 3, 2, 1]

Method 7: Reverse a string using stack

def create(): 
    stack1=[] 
    return stack1
   

def size(stack1): 
    return len(stack1) 
   

def isEmpty(stack1): 
    if size(stack1) == 0: 
        return true 
   

def push(stack1,element): 
    stack1.append(element) 
   

def pop(stack1): 
    if isEmpty(stack1): return
    return stack1.pop() 
   

def rev_string(input): 
    x = len(input) 
       
    
    stack1 = create() 
   
   
    for i in range(0,x,1): 
        push(stack1,input[i]) 
   
    
    input="" 
   
    
    for i in range(0,x,1): 
        input+=pop(stack1) 
           
    return input 
  

n = "STRING"
print ("Original string: ") 
print (n) 
print ("Reversed string: ") 
print (rev_string(n))

Output:

Original string:
STRING
Reversed string:
GNIRTS

References