How Does the = Operator Work in Python and How Can You Customize Its Behavior?

Understanding the Role of = in Python

Python provides a succinct and convenient = operator that performs a specific operation on data structures. It is a shortcut notation for a more complex sequence of operations.

Internally, = utilizes the iadd special method. If iadd is not defined for a particular class, it may instead delegate to add or __radd__.

Customizing the = Operation with iadd

The iadd method allows you to define custom behavior for the = operator. For example, consider the following class:

class Adder(object):
    def __init__(self, num=0):
        self.num = num

    def __iadd__(self, other):
        print(f'in __iadd__, {other}')
        self.num += other
        return self.num

In this class, each instance can be initialized with an integer, and the = operator can be used to accumulate numbers. By printing from within __iadd__, you can observe that it is called every time the operator is applied.

Example Usage

a = Adder(2)
a += 3
print(a)  # Output: 5

In this example, a = 3 is effectively equivalent to executing the following code:

def __iadd__(self, other):
    self.num = self.num + other

a.__iadd__(3)

Additional Resources for Python Shorthand Tools

For further exploration of similar Python shorthand tools, refer to the following resources:

• [Python Operators](https://www.w3schools.com/python/python_operators.asp)
• [Python Datatypes](https://www.w3schools.com/python/python_datatypes.asp)
• [Special Methods in Python](https://docs.python.org/3.10/reference/datamodel.html#special-method-names)

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