A question about Python Classes

Ethan Furman ethan at stoneleaf.us
Fri Apr 22 21:38:21 CEST 2011


Kyle T. Jones wrote:
> Ethan Furman wrote:
>> chad wrote:
>>> Let's say I have the following....
>>>
>>> class BaseHandler:
>>>     def foo(self):
>>>         print "Hello"
>>>
>>> class HomeHandler(BaseHandler):
>>>     pass
>>>
>>>
>>> Then I do the following...
>>>
>>> test = HomeHandler()
>>> test.foo()
>>>
>>> How can HomeHandler call foo() when I never created an instance of
>>> BaseHandler?
>>
>> You don't need to create an instance of BaseHandler.  You have the
>> class, Python knows you have the class -- Python will look there if the
>> subclasses lack an attribute.
>>
>> ~Ethan~
>>
> 
> Really?  That's not at all how I thought it worked in Python 
> (post-instantiation referencing of class and superclass code...)

I'm not sure exactly what you're asking/stating, but does this help?

8<---Py 3.2 code------------------------------------------
class BaseClass():
     def bFoo(self):
         print("Base foo here!")

class NormalClass(BaseClass):
     def nFoo(self):
         print("Normal foo here.")

class EnhancedClass(NormalClass):
     def eFoo(self):
         print("Enhanced foo comin' at ya!")

class EnrichedClass(EnhancedClass):
     def rFoo(self):
         print("Am I glowing yet?")

test = EnrichedClass()
test.bFoo()
test.nFoo()
test.eFoo()
test.rFoo()

def newFoo(self):
     print("Ha!  You've been replaced!")

BaseClass.bFoo = newFoo

test.bFoo()
8<----------------------------------------------------------



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