How do you print a reverse number in python?

Question

Example 1: Reverse a Number using a while loop

num = 1234
reversed_num = 0

while num != 0:
    digit = num % 10
    reversed_num = reversed_num * 10 + digit
    num //= 10

print("Reversed Number: " + str(reversed_num))

Output

Nội dung chính Show

Example 1: Reverse a Number using a while loop
Example 2: Using String slicing
Reverse a number using Python while loop
Reverse a Number Using Recursion
How do I print a reverse number?
How do you reverse a number backwards in Python?
How do you print a reverse number in Python while loop?

In this program, while loop is used to reverse a number as given in the following steps:

First, the remainder of the num divided by 10 is stored in the variable digit. Now, the digit contains the last digit of num, i.e. 4.
digit is then added to the variable reversed after multiplying it by 10. Multiplication by 10 adds a new place in the reversed number. One-th place multiplied by 10 gives you tenth place, tenth gives you hundredth, and so on. In this case, reversed_num contains 0 * 10 + 4 = 4.
num is then divided by 10 so that now it only contains the first three digits: 123.
After second iteration, digit equals 3, reversed equals 4 * 10 + 3 = 43 and num = 12.
After third iteration, digit equals 2, reversed equals 43 * 10 + 2 = 432 and num = 1.
After fourth iteration, digit equals 1, reversed equals 432 * 10 + 1 = 4321 and num = 0.
Now num = 0, so the test expression num != 0 fails and while loop exits. reversed already contains the reversed number 4321.

Example 2: Using String slicing

num = 123456
print(str(num)[::-1])

Output

Using the string slicing concept, you can get reverse the string. ::-1 corresponds to start:stop:step. When you pass -1 as step, the start point goes to the end and stop at the front.

It is the most asked programming question in the interview. We can reverse the integer number in Python using the different methods.

How do you print a reverse number in python?

Here we will write the program which takes input number and reversed the same. Let's understand the following methods of reversing the integer number.

Using while loop
Using recursion

Reverse a number using Python while loop

First, we understand the algorithm of this program. It will make easy to understand the program logic. Once you get the logic, you can write the program in any language, not only Python.

Algorithm

Let's implement the above algorithm in program.

Program

Output:

Enter the integer number: 12345
The reverse number is: 54321

Explanation -

Let's understand this program step by step.

We initialed a number variable for user input and variable revs_number initial value to null.

First Iteration

Reminder = number %10
Reminder = 12345%10 = 5
Reverse = Reverse *10 + Reminder Initial value of revs_number is null
Reverse = 0 * 10 + 5 = 0 + 5 = 5
Number = Number //10
Number = 1234 //10 = 1234 // Now loop will iterate on this number.

Second Iteration

Now the number is 123, and the revs_number is 5. The while checks its condition and executes for the next iteration.

Reminder = Number % 10
Reminder = 1234 % 10 = 4
Reverse = Reverse *10+ Reminder = 5 * 10 + 4
Reverse = 50 + 4 = 54
Number = Number //10 = 12345 //10
Number = 123

Third Iteration

From the Second Iteration, the values of both Number and Reverse have been changed as: number = 123 and revs_number = 54

Reminder = Number %10
Reminder = 123%10 = 3
Reverse = Reverse *10+ Reminder = 54 * 10 + 3
Reverse = 540 + 3 = 543
Number = Number //10 = 123//10
Number = 12

Fourth Iteration

The modified number is 12 and the revs_number is 543: Now while executes again.

Reminder = Number %10
Reminder = 12 %10 = 2
Reverse = Reverse *10+ Reminder = 543 * 10 + 2
Reverse = 5430 + 2 = 5432
Number = Number //10 = 12//10
Number = 1

Fifth Iteration

Reminder = Number %10
Reminder = 1 %1 0 = 1
Reverse = Reverse *10+ Reminder = 5432 * 10 + 1
Reverse = 54320 + 1 = 54321

while loop is terminated because if found the false as a Boolean result.

You can enter the different number and check the result.

Reverse a Number Using Recursion

Let's understand the following example.

Output:

Enter the number: 5426
The Reverse of entered number is = 6245

Logic is same in both programs. Once you understand the logic, it will easy to do it by own.

How do I print a reverse number?

Let's see a simple c example to reverse a given number..

#include.

int main().

int n, reverse=0, rem;.

printf("Enter a number: ");.

scanf("%d", &n);.

while(n!=0).

How do you reverse a number backwards in Python?

Reversing a number using reversed Method We use the python reversed() function to reverse a number by this method. This function returns a pointer that can iterate the string/list in reverse order. We use the join() method of python to obtain the reversed number from this iterator finally.