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
4321
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 variabledigit
. Now, thedigit
contains the last digit ofnum
, 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
contains0 * 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 equals4 * 10 + 3 = 43
andnum = 12
. - After third iteration,
digit
equals 2, reversed equals43 * 10 + 2 = 432
andnum = 1
. - After fourth iteration,
digit
equals 1, reversed equals432 * 10 + 1 = 4321
andnum = 0
. - Now
num = 0
, so the test expressionnum != 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
654321
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.
We will develop a program to
reverse a number in python using while loop. To reverse a number we need to extract the last digit of the number and add that number into a temporary variable with some calculation, then remove the last digit of the number. Do these processes until the number becomes zero. To remove the last digit the modulus operator [%] will be helpful for us, and to remove the last digit division operator [/] can be
used. To add the last digit first we need to multiply the previous value by 10. Once you get the logic, you can write the program in any language. Example of the reverse a number:- Procedure to find reverse of a number, We will take integer numbers while declaring the variables. Then, find the reverse of a number using the while loop and finally, the result will be displayed on the screen.
Number: 56021
Reverse number: 12065
# Python program to reverse a number using while loop
# take inputs
num = 12345
# calculate reverse of number
reverse = 0
while[num > 0]:
last_digit = num % 10
reverse = reverse * 10 + last_digit
num = num // 10
# display result
print['The reverse number is =', reverse]
Output:-
The reverse number is = 54321
Reverse a Number in Python using While Loop
In the previous program, inputs are hardcoded in the program but in this program, input will be provided by the user.
# Python program to reverse a number using while loop
# take inputs
num = int[input['Enter a number: ']]
# calculate reverse of number
reverse = 0
while[num > 0]:
last_digit = num % 10
reverse = reverse * 10 + last_digit
num = num // 10
# display result
print['The reverse number is =', reverse]
Output for the input values test-case-1:-
Enter a number: 416064
The reverse number is = 460614
Output for the input values test-case-2:-
Enter a number: 164532
The reverse
number is = 235461
Python Program to Reverse a Number using While Loop
We can also take the help of a function to reverse a number in python using while loop. A function is a block of code that performs a specific task.
# Python program to reverse a number using while loop
def findReverse[n]: #user-defined function
# calculate reverse of number
reverse = 0
reminder = 0
while[n != 0]:
remainder = n % 10
reverse = reverse * 10 + remainder
n = int[n / 10]
return reverse
# take inputs
num = int[input['Enter the number: ']]
# calling function and display result
reverse = findReverse[num]
print['The reverse number is =', reverse]
Output:-
Enter the number: 46894
The reverse number is = 49864