Question

Python (2.6) seems to be derping for no reason, can anyone see a problem with this code?

class DB ():
    def doSomething (self, str):
        print str

class A ():
    __db = DB()

    @staticmethod
    def getDB ():
        return A.__db

    db = property(getDB)


A.db.doSomething("blah")

Fails with the exception:

AttributeError: ‘property’ object has no attribute ‘doSomething’

It was my understanding that a property would automatically run its getter when accessed, so why is it complaining about a property object, and why isn’t it finding my clearly available method?

Answer 1

In addition to needing to inherit from object, properties only work on instances.

a = A()
a.db.doSomething("blah")

To make a property work on the class, you can define a metaclass. (A class is an instance of a metaclass, so properties defined on the metaclass work on the class, just as properties defined on a class work on an instance of that class.)