Python3.2 Official document Translation--instance objects and method objects

6.3.3Instance Object

What do we do with instance objects today? The only action available for an instance object is a property reference. There are now two legitimate property names: Data properties and methods.

Data properties are equivalent to instance variables in smallTalk , data members inC + + . Data attributes are not required to be declared. Like local coupling beam, they exist when they first assign values. For example, suppose x is an instance of the above created MyClass class, and the following code block indicates that the value will be printed . This value is no matter what the error.

X.counter = 1

While X.counter < 10:

X.counter = x.counter*2

Print (X.counter)

Del X.counter

An example of a method that is referenced by an instance property is a method. A method is a function that belongs to an object. (in python , the term method and the class instance are not unique): There are methods for other object types as well. For example,thelist object has a name of append,insert,remove,sort methods, and so on. However, in the ensuing discussion, unless specifically stated, we use the term method to use the object instance method. )

The legal method name of an instance object depends on its class. By definition, all function objects in a class define corresponding instance methods. So, in our example,x.f is a valid method reference, since myclass.f is a method, but x.i is not, because Myclass.i not. But unlike x.f and myclass.f , it is a method object, not a function object.

6.3.4Method Object

Typically, a method is called after it is bound.

X.F()

In the MyClass instance, it will return the string ' Hello World '. However, you do not need to call the method immediately: X.F is a method object that can be saved and then called later, such as:

XF = X.F

While True:

Print (XF ())

The Hello world will be printed continuously until the program terminates.

What happened in detail when the method was called? You may have noticed Although function definition f () x.f () is not called when the number of references is passed. What happened to the number? python when a function that requires a number of parameters is not invoked regardless of the number of parameters

In fact, you can test the answer: one of the characteristics of a method is that the instance object is passed to the function as the first parameter. In our example, thex.f() method is equivalent to myclass.f(x). in general, a call to include N The table is equivalent to the corresponding function, which includes a list that was created when the method object was first inserted.

Let's say you still don't have a clear picture of how the method works, and it's possible to make the truth clear. When an instance property refers to a property that is not a data attribute, its class is searchable. Suppose the name represents a legitimate function object property, and the method object is created by encapsulating the (pointer) instance object and the function object found in the abstract class. When a method object is called with a list parameter, a new table of parameters is created from the instance object and the list of references, and the function object is called with a new attribute listing.

Python3.2 Official document Translation--instance objects and method objects