Classic and New Style Classes?

[Chris S.]

I'm generating the source of an object from a list of objects. Therefore
I need to determine if the object is a class definition (i.e. 'def
something(whate ver):') or a class instance (i.e. 'somename =
somethingelse() '). With classic classes this is trivial, since all I
have to do is check the type. However, for the new "improved" style
classes this seems next to impossible, since everything is essentially
an instance of something.

isinstance(clas s, classinfo) won't work since I won't necessarily know
classinfo.

Is there any way to make this distinction? Any help is appreciated.

[Peter Otten]

Chris S. wrote:

I'm generating the source of an object from a list of objects. Therefore
I need to determine if the object is a class definition (i.e. 'def
something(whate ver):') or a class instance (i.e. 'somename =
somethingelse() '). With classic classes this is trivial, since all I
have to do is check the type. However, for the new "improved" style
classes this seems next to impossible, since everything is essentially
an instance of something.

isinstance(clas s, classinfo) won't work since I won't necessarily know
classinfo.

Is there any way to make this distinction? Any help is appreciated.

It's not clear to me why isinstance() wouldn't work:

import types
def f(): pass .... class T(object): pass .... class U: pass .... isinstance(T(), types.FunctionT ype) False isinstance(U(), types.FunctionT ype) False isinstance(f, types.FunctionT ype) True

Another option would be to use callable(), which also returns True for
classes and callable instances:
class V(object): .... def __call__(self): pass
.... callable(T) True callable(T()) False callable(V())

True

Peter

[Leif K-Brooks]

Chris S. wrote:

I'm generating the source of an object from a list of objects. Therefore
I need to determine if the object is a class definition (i.e. 'def
something(whate ver):') or a class instance (i.e. 'somename =
somethingelse() ').

I'm assuming you meant 'class something(whate ver):' rather than def. If
so, this should work:

class Foo(object): .... pass
.... isinstance(Foo, type) True isinstance(Foo( ), type)

False

[Michele Simionato]

"Chris S." <ch*****@NOSPAM udel.edu> wrote in message news:<cb******* ***@scrotar.nss .udel.edu>...

I'm generating the source of an object from a list of objects. Therefore
I need to determine if the object is a class definition (i.e. 'def
something(whate ver):') or a class instance (i.e. 'somename =
somethingelse() '). With classic classes this is trivial, since all I
have to do is check the type. However, for the new "improved" style
classes this seems next to impossible, since everything is essentially
an instance of something.

isinstance(clas s, classinfo) won't work since I won't necessarily know
classinfo.

Is there any way to make this distinction? Any help is appreciated.

from types import ClassType
class Old: pass .... isinstance(Old, ClassType) True class New(object): pass .... isinstance(New, type)

True

Also Old.__class__ raises an error whereas New.__class__ returns type(New).

Is this what you are asking for?

Michele Simionato

[Chris S.]

Michele Simionato wrote:

Also Old.__class__ raises an error whereas New.__class__ returns type(New).

Is this what you are asking for?

Michele Simionato

Yes, thanks a lot.

[Chris S.]

Leif K-Brooks wrote:

Chris S. wrote:

I'm assuming you meant 'class something(whate ver):' rather than def. If
so, this should work:

>>> class Foo(object): ... pass
... >>> isinstance(Foo, type) True >>> isinstance(Foo( ), type)

False

Yeah, minor typo. I needed to differentiate a class definition from a
class instance, and now I see using isinstance(obj, type) does the trick.
Thanks a lot.