Python Program to Reverse a Number

# Python Program to Reverse a Number

In this python tutorial, you will learn how to Reverse a Number using the if and else statements, while loop along with the different operators of the python programming language.

## How to Reverse a Number?

Let’s take a look at the first source code , here the values are given as input by the user in the code, the operators and while loop along with the assignment operators carry out the function.

```#Python Program to Reverse a Number using while loop

num =int(input("Enter the integer: "))
reversed_num = 0

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

print("\nReversed Number: " + str(reversed_num))```

INPUT:

`1234`

OUTPUT:

```Enter the integer:
Reversed Number: 4321```
1. Here we give the user the option to enter the values and the input values are scanned using the `input` function and are stored in the variable `num` with the statements/strings `("Enter the integer: ")`  , we use the `int`  function and declare the  input value as an integer value.
2. We assign the variable `reversed_num` with the integer `0`.
3. Next, we declare a `while` loop with the condition `num != 0` followed by a `:`, after which we declare the condition `digit = num % 10 `and  `reversed_num = reversed_num * 10 + digit` where `num //= 10`.
4. In this code, the while loop is iterated until the test expression `num != 0` is equal to `0`. During each iteration, the remainder of the  `num` divided by 10 is stored in the variable `digit`. During each iteration `digit` reduces by one and when the `while` loop exits , the reversed value is already in the variable `reversed_num`.
5. In the STDIN section of the code editor the input values are entered.
6. The final output values are displayed with the statement `("\nReversed Number: " + str(reversed_num))` using the `print` function, where the `+ str(reversed_num)` returns and displays the string version of the `reversed_num` value.

Let’s take a look at the second source code , here the values are given as input by the user in the code, inbuilt methods and print statement carry out the function.

```#Python Program to Reverse a Number using string slicing

num =int(input("Enter the integer: "))
print("\nReversed Number:",(str(num)[::-1]))
```

INPUT:

`123456`

OUTPUT:

```Enter the integer:
Reversed Number: 654321```
1. Here we give the user the option to enter the values and the input values are scanned using the `input` function and are stored in the variable `num` with the statements/strings `("Enter the integer: ")`  , we use the `int`  function and declare the  input value as an integer value.
2. In the STDIN section of the code editor the input values are entered.
3. The `print` function will display the statement `("\nReversed Number:",(str(num)[::-1]))` , where the function `(str(num)[::-1])` corresponds to `start:stop:step`
4. When you use `[::-1]` it starts from the end towards the first taking each element, so it reverses and will display the length of the value in string format which the variable `num` holds.

NOTE:

• The != operator is defined as not equal to operator. It returns True if operands on either side are not equal to each other, and returns False if they are equal.
• The % modulus operator functions returns modulus of the given arguments.
• The * multiplication operator returns product of the given arguments.
• The //= operator know as the double division assignment operator lets you divide two values together and assign the resultant value to a variable.
• The While true loop in python runs without any conditions until the break statement executes inside the loop.
• The colon : at the end of the if and else statement tells Python that the next line of code should only be run if the condition is true.
• The str() function in python returns the string version of the object.
• The statement for the input function are enclosed in single quotes and parenthesis.
• The \n in the code indicates a new line or the end of a statement line or a string.
• The print statement/string to be displayed in enclosed in double quotes.
• The input() function allows a user to insert a value into a program, it returns a integer value.
• The statement for the input function are enclosed in single quotes and parenthesis.