Introduction to Python functions: functions and examples of isinstance function

Introduction to Python functions: the role and examples of the isinstance function

As a high-level programming language, Python provides a wealth of built-in functions to simplify programming tasks. One of them is the isinstance function. The isinstance function is used to determine whether an object belongs to a specified type. This article will introduce the role and examples of the isinstance function and provide specific code examples.

The basic syntax of the isinstance function is as follows:
isinstance(object, classinfo)

Among them, the object parameter is the object to be judged, and the classinfo parameter can be a type or a type tuple. When the object object belongs to one of the classinfo type or classinfo type tuple, the function returns True; otherwise, it returns False.

Let’s look at a simple example to understand the role of the isinstance function:

# 示例1
num = 123
print(isinstance(num, int))  # True
print(isinstance(num, float))  # False

str_value = "hello"
print(isinstance(str_value, str))  # True
print(isinstance(str_value, int))  # False

person = {"name": "Alice", "age": 25}
print(isinstance(person, dict))  # True
print(isinstance(person, list))  # False

In the above example, we determined the types of an integer, a string and a dictionary object respectively. As you can see, the type of an object can be easily determined using the isinstance function.

Let’s look at a slightly more complex example to illustrate the application of the isinstance function in inheritance relationships:

# 示例2
class Animal:
    pass

class Dog(Animal):
    pass

class Cat(Animal):
    pass

dog = Dog()
cat = Cat()

print(isinstance(dog, Animal))  # True，因为Dog类继承自Animal类
print(isinstance(cat, Animal))  # True，因为Cat类继承自Animal类
print(isinstance(dog, Dog))  # True
print(isinstance(cat, Cat))  # True
print(isinstance(dog, Cat))  # False
print(isinstance(cat, Dog))  # False

In Example 2, we define an Animal class and derive The Dog class and the Cat class. Then we created an object dog of Dog type and an object cat of Cat type. We use the isinstance function to determine the relationship between these objects and the Animal, Dog, and Cat classes. It can be seen from the output that when an object is a specified class or a subclass of the class, the isinstance function returns True; otherwise, it returns False.

The application of the isinstance function is very flexible. It can be used to determine the type of the object and the relationship between the object and the class. When writing programs, we often need to adopt different logical processing according to different situations, and the use of the isinstance function can help us quickly and accurately determine the type of object, so as to choose the correct processing method.

Summary:
This article introduces the role and usage of the isinstance function, and demonstrates the specific application of the function through sample code. The isinstance function is a commonly used built-in function in Python, used to determine the type of an object. Its use is very simple, just pass in the object to be judged and the type to be judged as parameters. The flexible application of the isinstance function can help developers write programs more efficiently. I hope this article can help readers understand and use the isinstance function.

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