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This article mainly explains "what is the metaclass in Python". The content in the article is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "what is the metaclass in Python".

Xiaoming, xiaohong and xiaozhang are all students. This kind of group is called Student.

Common methods for Python to define classes, using the keyword class

In [36]: class Student (object):

...: pass

If xiaoming, xiaohong, and xiaozhang are instances of the class, then:

Xiaoming = Student ()

Xiaohong = Student ()

Xiaozhang = Student ()

After creation, the _ _ class__ property of xiaoming returns the Student class

In [38]: xiaoming.__class__

Out [38]: _ _ main__.Student

The question is, the Student class has a _ _ class__ attribute, and if so, what does it return?

In [39]: xiaoming.__class__.__class__

Out [39]: type

Wow, the program is correct. Return type.

So, we might as well guess: Student class, type is type

In other words, the Student class is an object whose type is type

So, everything in Python is an object, and a class is also an object.

In Python, the class that describes the Student class is called metaclass.

According to this logical extension, the class that describes metaclass is called metaclass, and the class that describes metaclass is also called metaclass.

Smart friends will ask, since the Student class can create an instance, can the type class create an instance? If it can, the instance it creates is called: class. You guys are so smart!

By the way, the type class must be able to create instances, such as the Student class.

In [40]: Student = type ('Student', (), {})

In [41]: Student

Out [41]: _ _ main__.Student

It is identical to the Student class created with the class keyword.

The class of Python, because it is an object again, is similar to the operation of xiaoming,xiaohong objects. Support:

Assignment copy add attribute as function parameter In [43]: StudentMirror = Student # class direct assignment # class direct assignment

In [44]: Student.class_property = 'class_property' # add class attributes

In [46]: hasattr (Student, 'class_property')

Out [46]: True

Metaclass, it is true that the use of not so much, perhaps first understand these, will be able to cope with some situations. Even Tim Peters, the leader of Python:

"Metaclass is deep magic, and 99% of users should not have to worry about it at all."

Thank you for your reading, the above is the content of "what is the metaclass in Python". After the study of this article, I believe you have a deeper understanding of what the metaclass in Python is, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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