Updated April 17, 2023
Introduction to Reverse Number in Python
Reverse operation in python can be defined as a process of turning the order of the input assigned to a variable from back to front or front to back. This operation can be achieved by any kind of logic involving the conditional statements of python, such as for loop, while conditional statement, if condition, etc. There are multiple pre-defined methods in python which can be worked along with the conditional statements for creating reverse logical function, and they are list method, slice method, recursion method, etc. Reverse() method is the straightforward method for performing this operation for any kind of input provided by the user.
Logic for Reverse Number in Python
The below points briefly us about how to reverse a given number in python:
- The input number can be read by using input () or raw_input () method.
- Next, check whether the entered value is an integer or not.
- Now check whether a given integer is greater than 0 or not.
- Create a variable called reverse and initialize the variable value with 0.
- Now find the remainder for the given input number by using the mod (%) operator.
- Multiply the variable reverse with 10 and add the remainder value to it.
- Now floor (floor division is performing the division operation and resulting value provides lower integer to the value) divide the given input number with 10.
- The given input number will become 0 at some point.
- Now repeat the steps 5, 6, 7 until you get the input number is not greater than zero.
- In the last step, display the variable in reverse.
Reversing the Number Using different ways in Python
Below are the different ways in Python:
1. Using Slicing Method
Code:
def reverse_slicing(s):
return s[::-1]
my_number = '123456'
if __name__ == "__main__":
print('Reversing the given number using slicing =', reverse_slicing(my_number))Execution Steps:
- Save the python code in your drive. (Here, we have used D drive for executing the programs)
- Now open the command prompt and locate your drive.
- Execute the program with the command as python program_name.py
- The python programs will be saved with .py extension.
Output:
2. Using For loop Method
Code:
def reverse_for_loop(s):
s1 = ''
for c in s:
s1 = c + s1
return s1
my_number = '123456'
if __name__ == "__main__":
print('Reversing the given number using for loop =', reverse_for_loop(my_number))Output:
3. While Loop Method
Code:
def reverse_while_loop(s):
s1 = ''
length = len(s) - 1
while length >= 0:
s1 = s1 + s[length]
length = length - 1
return s1
my_number = '123456'
if __name__ == "__main__":
print('Reversing the given number using while loop =', reverse_while_loop(my_number))
Output:
4. Using Reversed Method
Code:
def reverse(string):
string = "".join(reversed(string))
return string
my_number = "123456"
print ("The given number is : ",end="")
print (my_number)
print ("Reversing the given number using reversed is : ",end="")
print (reverse(my_number)) Output:
5. Using user-entered number and then reversing it
Code:
My_Number = int(input("Please provide the number to be reversed: "))
Reverse_Number = 0
while(My_Number > 0):
Reminder = My_Number %10
Reverse_Number = (Reverse_Number *10) + Reminder
My_Number = My_Number //10
print("Reverse of the provided number is = %d" %Reverse_Number)Output:
6. Two-Digit Reverse Method
Code:
My_Number = int(input("Please provide the number to be reversed: "))
Reverse_Number = 0
temp = Reverse_Number
Reminder = 1
for i in range (Reminder+1):
Reminder = My_Number %10
Reverse_Number = (Reverse_Number *10) + Reminder
My_Number = My_Number //10
print("Reverse of the provided number is = %d" %Reverse_Number)Output:
7. Three-Digit Reverse Method
Code:
My_Number = int(input("Please provide the number to be reversed: "))
Reverse_Number = 0
temp = Reverse_Number
Reminder = 1
for i in range (Reminder+2):
Reminder = My_Number %10
Reverse_Number = (Reverse_Number *10) + Reminder
My_Number = My_Number //10
print("Reverse of the provided number is = %d" %Reverse_Number)Output:
8. Without the Recursion Method
Code:
my_num=str(input("Enter the number to be reversed: "))
print("Reverse of the given number is: ")
print(my_num[::-1])Output:
9. With Recursion Method
Code:
def reverse(s):
if len(s) == 0:
return s
else:
return reverse(s[1:]) + s[0]
my_number = "123456789"
print ("The given number is : ",end="")
print (my_number)
print ("Reversing the given number using recursion is : ",end="")
print (reverse(my_number))Output:
10. Using Function Method
Code:
def rev_number(My_Number) :
reverse_num = 0
while(My_Number) :
Reminder = My_Number % 10
reverse_num = reverse_num* 10 + Reminder
My_Number //= 10
return reverse_num
if __name__ == "__main__" :
My_Number = int(input('Please provide the number to be reversed:: '))
print('Reverse of the provided number is: ', rev_number(My_Number))Output:
11. Using List Method
Code:
number = "123456789"
print ("The given number is : " + number)
#converting number into list
list1 = list(number)
#applying reverse method of list
list1.reverse()
#converting list into number
number = ''.join(list1)
print ("Reverse of the provided number is : " + number)Output:
12. Using the Stack Method
Code:
def create_stack():
#creating a list as stack and return it
stack = []
return stack
def push(stack,element):
#adding new element to list
stack.append(element)
def pop(stack):
#deleting the last element from the list
if len(stack) == 0:
return
return stack.pop()
def reverse(number):
#reversing the number by using stack's functions
num = len(number)
#creating empty list (stack)
stack = create_stack()
#inserting number into list
for i in range(0,num):
push(stack,number[i])
number = ""
#getting last element of the stack list
for i in range(0,num):
number = number + pop(stack)
return number
number1 = "123456789"
number2 = reverse(number1)
print ("The given number is : " + number1)
print ("Reverse of the given number is : " + number2)Output:
Conclusion
So far in this tutorial, we have learned to find the reverse number of a given number in python. This program runs only once, i.e. it asks the user to enter a number, find the reverse value, print and exit. We can also insert it into an infinite loop for continuous reading of a new number from the user. Put it in an infinite loop and check what’s going on.
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