Why does this code keep returning a 'has no attribute' error?

Question

My code is as follows, where sdl2ext.Entity is a third party class.

class Grid(sdl2ext.Entity):
    def __init__(self, world):
        self.w = 3
        self.h = 3
        super(Grid,self).__init__()

    def dump(self):
        print(self.w)

def run():
    world = sdl2ext.World()
    g = Grid(world)
    g.dump()

if __name__ == "__main__":
    run()

The specific error that I get is with the line print(self.w):

AttributeError: object ''Grid'' has no attribute ''w''

Is this something to do with not initialising the underlying base object, sdl2ext.Entity?

Why are you initializing the superclass after setting the private attributes? — Ignacio Vazquez-Abrams
– Ignacio Vazquez-Abrams, Commented Dec 22, 2013 at 23:59
Because of the answer given here: stackoverflow.com/questions/10670020/… . Specifically the definition for the CastSpell class given in the accepted answer. — patchwork
– patchwork, Commented Dec 23, 2013 at 0:01
You misunderstand. Why are you initializing the superclass after setting the private attributes, instead of before? — Ignacio Vazquez-Abrams
– Ignacio Vazquez-Abrams, Commented Dec 23, 2013 at 0:05
@Ignacio, in the accepted answer for that linked question, the superclass is initialised after the private attributes. I thought it was ok to do that. — patchwork
– patchwork, Commented Dec 23, 2013 at 0:06

stefanw · Accepted Answer · 2013-12-23 00:05:26Z

2

You should read the code of the paren class. The class overwrites many special methods, including __getattr__ which likely has something to do with your problem.

answered Dec 23, 2013 at 0:05

stefanw

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4 Comments

Martijn Pieters Over a year ago

__getattr__ is only called as a fallback; self.w is first looked up in the instance __dict__, __getattr__ is only consulted if it is not found there.

Martijn Pieters Over a year ago

See the __getattr__ documentation: Called when an attribute lookup has not found the attribute in the usual places (i.e. it is not an instance attribute nor is it found in the class tree for self)

patchwork Over a year ago

So @Martijn are you saying that getattr is not the problem?

Martijn Pieters Over a year ago

@patchwork: I am saying __getattr__ cannot be the problem.

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