Use Python's isinstance() function to determine whether an object belongs to a certain class

Use Python's isinstance() function to determine whether an object belongs to a certain class

In Python, we often need to determine whether an object belongs to a specific class. In order to facilitate category judgment, Python provides a built-in function isinstance(). This article will introduce the usage of isinstance() function and provide code examples.

The isinstance() function can determine whether an object belongs to the specified class or a derived class of the class. Its syntax is as follows:

isinstance(object, classinfo)

Among them, object is the object to be judged, and classinfo can be a single class or a tuple composed of classes. If the object belongs to one of the classes or its derived classes, the isinstance() function will return True; otherwise, it returns False.

The following is a simple example that demonstrates how to use the isinstance() function to determine the object type:

class Dog:
    def __init__(self, name):
        self.name = name

class Cat:
    def __init__(self, name):
        self.name = name

dog = Dog("旺财")
cat = Cat("小花")

print(isinstance(dog, Dog))  # 输出：True
print(isinstance(dog, Cat))  # 输出：False
print(isinstance(cat, (Dog, Cat)))  # 输出：True

In the above example, we defined two classes Dog and Cat, both There is an attribute name. Then we created a dog object and a cat object. Through the isinstance() function, we determine whether the dog object belongs to the Dog class, whether the cat object belongs to the Cat class, and whether the cat object belongs to the Dog class or the Cat class.

In addition to determining the type of a single object, the isinstance() function can also determine whether an object belongs to any one of multiple classes.

It is worth noting that the isinstance() function can also be used to determine the inheritance relationship of the object type. That is to say, if a class inherits another class, the isinstance() function can determine whether the object belongs to the parent class or subclass.

The following is a more complex example that demonstrates the inheritance judgment of the isinstance() function:

class Animal:
    pass

class Mammal(Animal):
    pass

class Dog(Mammal):
    def __init__(self, name):
        self.name = name

class Cat(Mammal):
    def __init__(self, name):
        self.name = name

dog = Dog("旺财")
cat = Cat("小花")

print(isinstance(dog, Dog))  # 输出：True
print(isinstance(dog, Mammal))  # 输出：True
print(isinstance(dog, Animal))  # 输出：True
print(isinstance(cat, Mammal))  # 输出：True
print(isinstance(cat, Animal))  # 输出：True
print(isinstance(dog, Cat))  # 输出：False

In the above example, we defined an Animal class and a Mammal class as the parent class , and then defined the Dog class and Cat class as subclasses of the Mammal class. Through the isinstance() function, we determine whether the dog object belongs to the Dog class, Mammal class and Animal class, whether the cat object belongs to the Mammal class and Animal class, and whether the dog object belongs to the Cat class.

Through the introduction of this article, we can see that we can easily determine whether an object belongs to a specific class through the isinstance() function. In actual development, mastering the usage of the isinstance() function can help us handle object type judgment and processing logic more flexibly. If you are interested in Python's category judgment, you may wish to practice using the isinstance() function in an actual project. I believe it will be helpful to your programming skills.

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