## 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 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**

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.

**Also Read:**