Table of Contents
In this example, you will learn to reverse a number.
To understand this example, you should have the knowledge of the following Python programming topics:
1. 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.
2. 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.
Related posts:
Python Program to Create Pyramid Patterns
Python Set symmetric_difference_update()
Python pass statement
Python frozenset()
Python Program to Display Calendar
Python Variables, Constants and Literals
Python String translate()
Java Program to Implement the Program Used in grep/egrep/fgrep
Python List sort()
Python String isupper()
Python int()
Python Program to Merge Mails
Python String format_map()
Python Tuple
Python Program to Delete an Element From a Dictionary
Python String title()
Python globals()
Python String isdecimal()
Debug a JavaMail Program
Python Program to Check Whether a String is Palindrome or Not
Python String splitlines()
Python List count()
Python String isidentifier()
Python classmethod()
Python Program to Iterate Through Two Lists in Parallel
Python Program to Check If Two Strings are Anagram
Python sleep()
Python Recursion
Python Set add()
Python List remove()
Python Set intersection()
Python Program to Find Numbers Divisible by Another Number