How to use the __mul__() function in Python to define the multiplication operation of two objects

How to use __mul__()Function to define the multiplication operation of two objects

Introduction

Python is a An object-oriented programming language that provides many special methods (special double underline methods or magic methods) for customizing the behavior of objects. Among them, the __mul__() method can be used to define the multiplication operation of two objects. In this article, we will learn how to use the __mul__() method to define the multiplication operation of a custom class.

__mul__()Method introduction

__mul__()Method is a special method in Python, used to define the multiplication of two objects operate. When we multiply two objects, the Python interpreter automatically calls the __mul__() method and passes the first object as a parameter to the method. __mul__()The method needs to return the result of multiplying two objects.

Code Example

The following is a simple code example that demonstrates how to use the __mul__() method to define a multiplication operation for a custom class:

class Number:
    def __init__(self, value):
        self.value = value

    def __mul__(self, other):
        if isinstance(other, Number):
            return Number(self.value * other.value)
        elif isinstance(other, int) or isinstance(other, float):
            return Number(self.value * other)
        else:
            raise TypeError("Unsupported operand type for *: '{}' and '{}'".format(
                type(self).__name__, type(other).__name__))

    def __repr__(self):
        return "Number({})".format(self.value)


# 创建两个Number对象
num_1 = Number(2)
num_2 = Number(3)

# 两个Number对象相乘
result_1 = num_1 * num_2
print(result_1)  # 输出结果: Number(6)

# Number对象和整数相乘
result_2 = num_1 * 4
print(result_2)  # 输出结果: Number(8)

In the above code, we defined a custom class named Number and implemented the __mul__() method in this class. This method receives a other parameter, which represents the second object to be multiplied. Depending on the type of the other parameter, we implement different multiplication logic:

• If the other parameter is a Number object, We multiply the value of two objects and return a new Number object.
• If the other parameter is an integer or floating point number, we multiply the Number object's value by this number and return a new The Number object.
• If the other parameter is an object of another type, we will throw a TypeError, indicating that the multiplication operation of this type is not supported.

Finally, we create two Number objects at the end of the sample code and multiply them with another Number object and an integer respectively. . The printout shows that we successfully defined the multiplication operation for Number objects.

Summary

By using the __mul__() method, we can customize the multiplication operation of the class. By determining the type of the second operand, we can implement different multiplication logic. When we multiply objects of a custom class, the Python interpreter will automatically call the __mul__() method and pass the first object as a parameter to the method.

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