Question

What is the difference between the following class methods?

Is it that one is static and the other is not?

class Test(object):   def method_one(self):     print 'Called method_one'    def method_two():     print 'Called method_two'  a_test = Test() a_test.method_one() a_test.method_two() 

Answer 1

In Python, there is a distinction between bound and unbound methods.

Basically, a call to a member function (like method_one), a bound function

a_test.method_one() 

is translated to

Test.method_one(a_test) 

i.e. a call to an unbound method. Because of that, a call to your version of method_two will fail with a TypeError

>>> a_test = Test()  >>> a_test.method_two() Traceback (most recent call last):   File '<stdin>', line 1, in <module> TypeError: method_two() takes no arguments (1 given)  

You can change the behavior of a method using a decorator

class Test(object):     def method_one(self):         print 'Called method_one'      @staticmethod     def method_two():         print 'Called method two' 

The decorator tells the built-in default metaclass type (the class of a class, cf. this question) to not create bound methods for method_two.

Now, you can invoke static method both on an instance or on the class directly:

>>> a_test = Test() >>> a_test.method_one() Called method_one >>> a_test.method_two() Called method_two >>> Test.method_two() Called method_two