type() for new style classes - buggy?

[Michal Vitecek]

hello,

does the type() command work correctly for new style classes? i guess
it does not, unfortunately. for example, for a new style class'
instance it returns <class '__main__.Class Name'>, but for old style
class' instance it returns <type 'instance'>.
[color=blue][color=green][color=darkred]
>>> import types
>>> class A(object):[/color][/color][/color]
pass[color=blue][color=green][color=darkred]
>>> class B:[/color][/color][/color]
pass[color=blue][color=green][color=darkred]
>>> type(A())[/color][/color][/color]
<class '__main__.A'>[color=blue][color=green][color=darkred]
>>> type(B())[/color][/color][/color]
<type 'instance'>[color=blue][color=green][color=darkred]
>>> type(A()) == types.InstanceT ype[/color][/color][/color]
0[color=blue][color=green][color=darkred]
>>> type(B()) == types.InstanceT ype[/color][/color][/color]
1

how can one then determine what he's working with when he uses new
style classes (either instance or class)?

thank you,
--
fuf (fuf@mageo.cz)

[Sidharth Kuruvila]

Re: type() for new style classes - buggy?



In the case of new style classes type actually doubles up as a class
constructor, so all classes including type itself are instances type.
[color=blue][color=green][color=darkred]
>>> class A(object):[/color][/color][/color]
.... pass
....[color=blue][color=green][color=darkred]
>>> a = A()
>>> type(a)[/color][/color][/color]
<class '__main__.A'>[color=blue][color=green][color=darkred]
>>> type(A)[/color][/color][/color]
<type 'type'>[color=blue][color=green][color=darkred]
>>> isinstance(A, type)[/color][/color][/color]
True[color=blue][color=green][color=darkred]
>>> isinstance(a, type)[/color][/color][/color]
False[color=blue][color=green][color=darkred]
>>> isinstance(type , type)[/color][/color][/color]
True[color=blue][color=green][color=darkred]
>>>[/color][/color][/color]

hope this helps
there is some documentation on new style classes you might want to read.

http://www.python.org/doc/newstyle.html

particularly the first essay by Guido.