Defining Class Attributes and Methods

Any variable that is bound in a class is a class attribute. Any function defined within a class is a method. Methods receive an instance of the class, conventionally called self, as the first argument. For example, to define some class attributes and methods, you might enter the following code:

class MyClass
    attr1 = 10        #class attributes
    attr2 = "hello"

    def method1(self):
        print MyClass.attr1   #reference the class attribute

    def method2(self):
        print MyClass.attr2   #reference the class attribute

    def method3(self, text):
        self.text = text        #instance attribute
        print text, self.text   #print my argument and my attribute

    method4 = method3   #make an alias for method3

Inside a class, you should qualify all references to class attributes with the class name; for example, MyClass.attr1. All references to instance attributes should be qualified with the self variable; for example, self.text. Outside the class, you should qualify all references to class attributes with the class name (for example MyClass.attr1) or with an instance of the class (for example x.attr1, where x is an instance of the class). Outside the class, all references to instance variables should be qualified with an instance of the class; for example, x.text.