python OOP, accessing attributes

Question

Why do i get an "AttributeError: 'NewOne' object has no attribute 'self.b'" error message when i try to access the attribute 'self.b' from the NewOne class. I mean it's right there.

class NewOne(object):  
    def __init__(self):
        self.b = 'Cat' # this is what i want to access
    def child(self):
        self.c = 'kitten'
        return self.c

class FatherClass(object):
    def __init__(self, a):
        self.a = a
    def son(self):
        self.i = 'I and my father'
        return self.i
    def father(self):
        self.x = 'are one'
        return self.x
    def father_son(self):
        u = NewOne()
        k = getattr(u, 'self.b') #why does it tell me NewOne has no self.b attr
        return self.a, k()

Isn't getattr used to access a method? Why is it called getattr and not getmeth or something? Thanks

mouad · Accepted Answer · 2011-01-20 14:47:57Z

6

replace this:

k = getattr(u, 'self.b')

by this:

k = getattr(u, 'b')

or even better just do:

k = u.b

answered Jan 20, 2011 at 14:47

mouad

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3 Comments

kassold Over a year ago

Thank you, thank you, thank you! what happens if an attribute and a method have the same name?

Andrew Jaffe Over a year ago

An attribute and a method cannot have the same name. More precisely, a method is an attribute, just one that is callable.

mouad Over a year ago

you're very welcome, it get overwrite by the last one that get defined, try it and see :)

Sven Marnach · Accepted Answer · 2011-01-20 14:47:55Z

2

Youe should write

k = getattr(u, 'b')

or better

k = u.b

instead.

The name of the attribute is b, not self.b. And usually you access attributes via obj.attr -- the getattr() form is only needed if the name of the attribute is dynamic (i.e. not known at the time you write the code, but computed at run time).

answered Jan 20, 2011 at 14:47

Sven Marnach

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1 Comment

kassold Over a year ago

"the getattr() form is only needed if the name of the attribute is dynamic" That's illuminating. Thank you.

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