In this post, we will learn number system conversion in Python using built-in functions with detailed explanations and examples.

There are many built-in functions in Python that help us convert decimal numbers to binary, octal, and hexadecimal numbers, or vice-versa. Let’s learn each of these functions with the help of examples.

## bin() Function

The

function is used to convert decimal integers into their respective binary representation.**bin()**

```
num = int(input("Enter a number: "))
binary = bin(num)
print(f"Binary of {num} is : {binary}")
```

**Output:**

```
Enter a number: 10
Binary of 10 is : 0b1010
```

The first two characters ** 0b** represent that it is a binary number and the remaining character

**is the actual binary representation of the given number.**

`1010`

## oct() function

The

function is used to convert decimal integers into their respective octal representation.**oct()**

```
num = int(input("Enter a number: "))
octal = oct(num)
print(f"Octal of {num} is : {octal}")
```

**Output:**

```
Enter a number: 10
Octal of 10 is : 0o12
```

As we already discussed, the first two characters ** 0o** represent that it is an octal number, and the remaining

**is the actual octal representation of given number.**

`12`

## hex() function

The

function is used to convert decimal integers into their respective hexadecimal representations.**hex()**

```
num = int(input("Enter a number: "))
hexadeciaml = hex(num)
print(f"Hexadeciaml of {num} is : {hexadeciaml}")
```

**Output:**

```
Enter a number: 10
Hexadeciaml of 10 is : 0xa
```

The first two characters ** 0x** represent that it is a hexadecimal number and the remaining character

**is the actual hexadecimal representation of the given number.**

`a`

Now let’s discuss how we can convert any binary, octal, and hexadecimal number into their respective decimal numbers.

## Binary to Decimal Number

We use the ** int()** function to convert any binary number into its respective decimal number. There is one attribute of the

**function called**

`int()`

**that helps us convert any number system into its respective decimal number.**

`base`

If you want to convert a binary number into a decimal number, you can achieve this by simply changing the ** base=2** in the

**function by default**

`int()`

**is set to 10. But remember one thing You have to pass a binary number or another number system such as an octal or hexadecimal number in the form of a string otherwise you will get an error.**

`base`

```
binary = "10"
decimal = int(binary,base=2)
print(f"Decimal of binary number {binary} is: {decimal}")
```

**Output:**

`Decimal of binary number 10 is: 2`

## Octal to Decimal Number

To convert an octal number to its respective decimal representation, pass the octal number as a string to the ** int()** function and set the

**to 8.**

`base`

```
octal = "12"
decimal = int(octal,base=8)
print(f"Decimal of octal number {octal} is: {decimal}")
```

**Output:**

`Decimal of octal number 12 is: 10`

## Hexadecimal to Decimal Number

To convert a hexadecimal number to its respective decimal representation, pass the hexadecimal number as a string to the ** int()** function and set the

**to 16.**

`base`

```
hexadecimal = "a"
decimal = int(hexadecimal,base=16)
print(f"Decimal of hexadecimal number {hexadecimal} is: {decimal}")
```

**Output:**

`Decimal of hexadecimal number a is: 10`

## Summary

For more Python programs click here 👉 60+ Python programs with an explanation