# Ashutosh Writes # bin() function in Python

## Introduction

The `bin()` function converts and returns the binary equivalent string of a given integer. If the parameter isn't an integer, it has to implement `__index__()` method to return an integer.

The syntax of `bin()` method is:

``````bin(num)
``````

where num is an integer number whose binary equivalent is to be calculated.

Note: In Python, a binary number is represented as a string prefixed with 0b.

## Case 1: Integer to Binary

``````num = 3
print(bin(num))
``````

Output:

``````0b11
``````

## Case 2: Object to Binary

In the case of Objects, we need to implement the `__index__()` method to get the binary equivalent string for an object.

``````class Money:
ten_rupee_note = 3
fifty_rupee_note = 5
hundred_rupee_note = 7

def __index__(self):
return (10*self.ten_rupee_note) + (50*self.fifty_rupee_note) + (100*self.hundred_rupee_note)

money = Money()
print(f"Total Money: {money.__index__()}")
print(f"Total Money in Binary: {bin(money)}")
``````

Output:

``````Total Money: 980
Total Money in Binary: 0b1111010100
``````

Here, we've created a Money class with three attributes - `ten_rupee_note`, `fifty_rupee_note`, and `hundred_rupee_note`. The `__index__()` method returns the total money, i.e. the sum of notes multiplied with their respective valuation. We then pass an object of the Money class to the binary function which returns the binary equivalent string of the integer returned by the `__index__()` method.

## Case 3: Raises Exception

``````class Money:
ten_rupee_note = 3
fifty_rupee_note = 5
hundred_rupee_note = 7

money = Money()
print(f"Total Money in Binary: {bin(money)}")
``````

In the previous example, if we don't implement the `__index__()`method, we'll get a TypeError.

Output:

``````Traceback (most recent call last):
File "D:\Quarantine\Test\Blog-Codes\Built-Ins\bin\error.py", line 8, in <module>
print(f"Total Money in Binary: {bin(money)}")
TypeError: 'Money' object cannot be interpreted as an integer
``````

## Conclusion

In this part, we learned about the Python `bin()` function with the help of examples. You can check out this tool to convert to binary.