python - 需要有关 Python 中类和实例概念的帮助

Question

我已经阅读了几篇文档，但“类”和“实例”的定义对我来说还不是很清楚。

看起来“类”就像返回某些结果的函数或方法的组合，对吗？那实例呢？我读到过您使用通过实例创建的类，但直接使用该类不是更容易吗？

有时获得语言的概念比使用它更难。

Answer 1

你的问题确实相当广泛，因为类和实例/对象是面向对象编程的重要部分，所以这并不是 Python 特有的。我建议您购买一些这方面的书籍，因为虽然最初是基础知识，但它可以变得非常深入。 In essense , 然而:

The most popular and developed model of OOP is a class-based model, as opposed to an object-based model. In this model, objects are entities that combine state (i.e., data), behavior (i.e., procedures, or methods) and identity (unique existence among all other objects). The structure and behavior of an object are defined by a class, which is a definition, or blueprint, of all objects of a specific type. An object must be explicitly created based on a class and an object thus created is considered to be an instance of that class. An object is similar to a structure, with the addition of method pointers, member access control, and an implicit data member which locates instances of the class (i.e. actual objects of that class) in the class hierarchy (essential for runtime inheritance features).

例如，您可以定义一个 Dog 类，并创建特定狗的实例:

>>> class Dog():
...     def __init__(self, name, breed):
...             self.name = name
...             self.breed = breed
...     def talk(self):
...             print "Hi, my name is " + self.name + ", I am a " + self.breed
...
>>> skip = Dog('Skip','Bulldog')
>>> spot = Dog('Spot','Dalmatian')
>>> spot.talk()
Hi, my name is Spot, I am a Dalmatian
>>> skip.talk()
Hi, my name is Skip, I am a Bulldog

虽然这个例子很愚蠢，但您可以开始了解如何定义一个 Client 类，该类为 Client 是什么设置蓝图，具有在特定客户端上执行操作的方法，然后操作通过创建对象并在该上下文中调用这些方法来创建客户端的特定实例。

然而，有时您有一个类的方法，通过类的实例访问这些方法并没有真正的意义，而更多的是从类本身访问。这些被称为 static methods .