Variable naming in Python

A review:

Two global variables (including functions and classes):

(1) Normal variable x:

* Can be used via module.x.

* Can be used with the From module import *.

(2) Start with "_" Variable x:

* Can be used via module.x.

* cannot be used through the From module import *.

* Can be used with the From module import x.

(3) Start with "__":

* Can be used via module.x.

* cannot be used through the From module import *.

* Can be used with the From module import x.

(4) "__all__" variable:

*from Module Import *, only the variables defined in __all__ are imported.

* If you put the _ start variable into __all__, it will be imported.

Variables in three categories:

(1) Variable of class :

* Double underscore (__) variables and functions represent private variables and methods of a class, and can only be called within a class method. Note: Do not write the double underline in the back.

* But a single underline can still be called, and a single underline is only a convention.

(2) The variable of the instance:

* Variables of the same type.

Variable naming in Python