How can a method directly access its class variables without using self?-CodePudding

I recently switched to Python from Java for development and is still not used to some of the implicitness of Python programming.

I have a class which I have defined some class variables, how can I access the class variables within a method in Python?

class Example:
    CONSTANT_A = "A"
    
    @staticmethod
    def mymethod():
        print(CONSTANT_A)

The above code would give me the error message: "CONSTANT_A" is not defined" by Pylance.

I know that I can make this work using self.CONSTANT_A, but self is referring to the Object, while I am trying to directly access to the Class variable (specifically constants).

Question

How can I directly access Class variables in Python and not through the instance?

CodePudding user response：

In python, you cannot access the parent scope (class)'s fields from methods without self. or cls..

Consider using classmethod:

class Example:
    CONSTANT_A = "A"
    
    @classmethod
    def mymethod(cls):
        print(cls.CONSTANT_A)

or directly accessing it like Classname.attribute:

class Example:
    CONSTANT_A = "A"
    
    @staticmethod
    def mymethod():
        print(Example.CONSTANT_A)

CodePudding user response：

for static method, you can access the class variable by <class_name>.<variable>.

>>> class Example:
...     CONSTANT_A = "A"
...     @staticmethod
...     def mymethod():
...         print(Example.CONSTANT_A) 
... 
>>> 
>>> x = Example.mymethod()
A # print value