24
>>> class Foo:
...   'it is a example'
...   print 'i am here'
... 
i am here
>>> Foo.__name__
'Foo'
>>> Foo().__name__
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: Foo instance has no attribute '__name__'
>>> Foo.__doc__
'it is a example'
>>> Foo().__doc__
'it is a example'
>>> Foo.__dict__
{'__module__': '__main__', '__doc__': 'it is a example'}
>>> Foo().__dict__
{}
>>> Foo.__module__
'__main__'
>>> Foo().__module__
'__main__'
>>> myname=Foo()
>>> myname.__name__
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
AttributeError: Foo instance has no attribute `__name__`

What is the reason instances have no attribute __name__?
maybe it is ok that the __name__ of instance-myname is myname.
would you mind tell me more logical, not the unreasonable grammar rules?

boatcoder
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showkey
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    What makes you think there is supposed to be a `__name__` attribute on instances? The [relevant documentation](http://docs.python.org/2/reference/datamodel.html) says it exists for classes (and other things), but I don't see any mention of it for instances. – Celada Jan 25 '13 at 03:27
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    From the [docs](http://docs.python.org/2/library/stdtypes.html?highlight=__name__#class.__name__): `__name__` is the name of a "class or type", not an instance of a class or type. Why should instances have `__name__`s? – Joel Cornett Jan 25 '13 at 03:29
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    Did you mean `Foo().__class__.__name__` ? – Ashwini Chaudhary Jan 25 '13 at 03:30

1 Answers1

31

You're seeing an artifact of the implementation of classes and instances. The __name__ attribute isn't stored in the class dictionary; therefore, it can't be seen from a direct instance lookup.

Look at vars(Foo) to see that only __module__ and __doc__ are in the class dictionary and are visible to the instance.

For the instance to access the name of a class, it has to work its way upward with Foo().__class__.__name__. Also note that classes have other attributes such as __bases__ that aren't in the class dictionary and likewise cannot be directly accessed from the instance.

Stefan van den Akker
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Raymond Hettinger
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  • I understand that is is dynamically set on the class during runtime. However, my IDE (PyCharm) is complaining about this error. Is there any way to avoid this without disabling Type checking? – physicalattraction Jun 09 '17 at 09:22