Overriding class variables in python

Question

I\'m trying to understand a bit how Python (2.6) deals with class, instances and so on, and at a certain point, I tried this code:

#/usr/bin/python2.6

class Bas         


        

Answer 1

The class variable is being overwritten. Try

@classmethod
def showDefaultValue(cls):
    print "defl == %s" % (cls.default,)

The reason your way doesn't work has more to do with the way Python treats default arguments to functions than with class attributes. The default value for defl is evaluated at the time Python defines the binding for showDefaultValue and this is done exactly once. When you call your method the default value used is what was evaluated at the time of definition.

In your case, defl was bound to the value of the default variable as it was during the execution of the class body form of Base. Regardless of how you call showDefaultValue later on (i.e., whether via Base or via Descend) that value remains fixed in all subsequent invocations of showDefaultValue.