Python的类方法

I used to work with PHP and recently I was asking myself, whats going on with this classmethod? Python manual is very technical and very short in words so it wont help with understanding that feature. I was googling and googling and I found answer -> http://code.anjanesh.net/2007/12/python-classmethods.html.

If you are lazy to click it. My explanation is shorter and below. :)

in PHP (maybe not all of you know PHP, but this language is so straight forward that everybody should understand what I'm talking about) we have static variables like this:

class A
{


    static protected $inner_var = null;


    static public function echoInnerVar()

    {

        echo self::$inner_var."\n";

    }


    static public function setInnerVar($v)

    {

        self::$inner_var = $v;

    }

}

class B extends A
{
}


A::setInnerVar(10);

B::setInnerVar(20);


A::echoInnerVar();

B::echoInnerVar();

The output will be in both cases 20.

However in python we can add @classmethod decorator and thus it is possible to have output 10 and 20 respectively. Example:

class A(object):

    inner_var = 0


    @classmethod

    def setInnerVar(cls, value):

        cls.inner_var = value


    @classmethod

    def echoInnerVar(cls):

        print cls.inner_var


class B(A):

    pass



A.setInnerVar(10)

B.setInnerVar(20)


A.echoInnerVar()

B.echoInnerVar()

Smart, ain't?