Getting a class name

[Harlin Seritt]

Hi,

How does one get the name of a class from within the class code? I
tried something like this as a guess:

self.__name__

Obviously it didn't work.

Anyone know how to do that?

Thanks,

Harlin

[deelan]

Harlin Seritt wrote:

Hi,

How does one get the name of a class from within the class code? I
tried something like this as a guess:

self.__name__

Get the class first, then inspect its name:

>>class Foo(object): pass

....

>>f = Foo()
f.__class__._ _name__

'Foo'

>>>

HTH
--
d.

[goodwolf]

I suppose that you wont get class name into its code (or before
definition end) but not into a method definition.
import sys

def getCodeName(dea p=0):
return sys._getframe(d eap+1).f_code.c o_name
class MyClass (object):
name = getCodeName() + '!'

[Gabriel Genellina]

En Sun, 18 Feb 2007 04:20:33 -0300, goodwolf <Ro**********@g mail.com>
escribió:

I suppose that you wont get class name into its code (or before
definition end) but not into a method definition.
import sys

def getCodeName(dea p=0):
return sys._getframe(d eap+1).f_code.c o_name
class MyClass (object):
name = getCodeName() + '!'

What's the advantage over MyClass.__name_ _?

--
Gabriel Genellina

[Fuzzyman]

On Feb 17, 8:33 pm, deelan <[e-mail] te:

Harlin Seritt wrote:

Hi,

How does one get the name of a class from within the class code? I
tried something like this as a guess:

self.__name__

Get the class first, then inspect its name:

>>class Foo(object): pass

...

>>f = Foo()
>>f.__class__._ _name__

'Foo'

>>>

Why is the __name__ attribute not available to the instance? Why don't
normal lookup rules apply (meaning that a magic attribute will be
looked up on the class for instances) ?

Fuzzyman
http://www.voidspace.org.uk/python/articles.shtml

HTH

--
d.

[Daniel Klein]

On 18 Feb 2007 04:24:47 -0800, "Fuzzyman" <fu******@gmail .comwrote:

>On Feb 17, 8:33 pm, deelan <[e-mail] te:

>Harlin Seritt wrote:

Hi,

How does one get the name of a class from within the class code? I
tried something like this as a guess:

self.__name__

Get the class first, then inspect its name:

> >>class Foo(object): pass

...

> >>f = Foo()
f.__class__._ _name__

'Foo'

> >>>

Why is the __name__ attribute not available to the instance? Why don't
normal lookup rules apply (meaning that a magic attribute will be
looked up on the class for instances) ?

Good question!

>>f = Foo()
dir(f)

['__class__', '__delattr__', '__dict__', '__doc__',
'__getattribute __', '__hash__', '__init__', '__module__', '__new__',
'__reduce__', '__reduce_ex__' , '__repr__', '__setattr__', '__str__',
'__weakref__']

>>dir(f.__class __)

['__class__', '__delattr__', '__dict__', '__doc__',
'__getattribute __', '__hash__', '__init__', '__module__', '__new__',
'__reduce__', '__reduce_ex__' , '__repr__', '__setattr__', '__str__',
'__weakref__']

>>>

Where is '__name__' ?
Dan

[Michele Simionato]

On Feb 18, 1:24 pm, "Fuzzyman" <fuzzy...@gmail .comwrote:

Why is the __name__ attribute not available to the instance? Why don't
normal lookup rules apply (meaning that a magic attribute will be
looked up on the class for instances) ?

Because __name__ isn't really an attribute, it is a descriptor defined
on
the metaclass:

>>type(type.__d ict__['__name__'])

<type 'getset_descrip tor'>

See http://users.rcn.com/python/download/Descriptor.htm for a guide to
descriptors, and the papers by me and David Mertz for a guide to
metaclasses.

Michele Simionato

[Fuzzyman]

On Feb 18, 1:22 pm, "Michele Simionato" <michele.simion [e-mail]>
wrote:

On Feb 18, 1:24 pm, "Fuzzyman" <fuzzy...@gmail .comwrote:

Why is the __name__ attribute not available to the instance? Why don't
normal lookup rules apply (meaning that a magic attribute will be
looked up on the class for instances) ?

Because __name__ isn't really an attribute, it is a descriptor defined
on
the metaclass:

>type(type.__di ct__['__name__'])

<type 'getset_descrip tor'>

Seehttp://users.rcn.com/python/download/Descriptor.htmf or a guide to
descriptors, and the papers by me and David Mertz for a guide to
metaclasses.

Thanks, I'll do some more reading.

I got as far as this on my own:

My guess is that it is because magic attributes are looked up on the
class. When you ask the *class* what its name is, the metaclass
answers on its behalf.

The class has no real ``__name__`` attribute, so when you ask the
instance (which doesn't inherit from the metaclass) you get an
``AttributeErro r``. Is this right ? In which case, how does the
metaclass (typically ``type`` which has many instance) know which
answer to supply ?

A simple test indicates that the name *is* looked up on the
metaclass :

... raw:: html

{+coloring}

>>class meta(type):

... __name__ = 'fish'
...

>>class Test(object):

... __metaclass__ = meta
...

>>Test.__name __

'fish'
{-coloring}

So maybe ``__name__`` is a propery and ``type`` keeps a dictionary of
instances to names, registered in ``type.__new__` ` ?

Fuzzyman
http://www.voidspace.org.uk/python/articles.shtml

Michele Simionato

[goodwolf]

On Feb 18, 9:17 am, "Gabriel Genellina" <gagsl...@yahoo .com.arwrote:

En Sun, 18 Feb 2007 04:20:33 -0300, goodwolf <Robert.Ka...@g mail.com>
escribió:

I suppose that you wont get class name into its code (or before
definition end) but not into a method definition.

import sys

def getCodeName(dea p=0):
return sys._getframe(d eap+1).f_code.c o_name

class MyClass (object):
name = getCodeName() + '!'

What's the advantage over MyClass.__name_ _?

--
Gabriel Genellina

>>class C(object):

.... name = C.__name__
....
Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "<stdin>", line 2, in C
NameError: name 'C' is not defined

>>>

[Gabriel Genellina]

En Sun, 18 Feb 2007 14:14:41 -0300, goodwolf <Ro**********@g mail.com>
escribió:

On Feb 18, 9:17 am, "Gabriel Genellina" <gagsl...@yahoo .com.arwrote:

>En Sun, 18 Feb 2007 04:20:33 -0300, goodwolf <Robert.Ka...@g mail.com>
escribió:

I suppose that you wont get class name into its code (or before
definition end) but not into a method definition.

import sys

def getCodeName(dea p=0):
return sys._getframe(d eap+1).f_code.c o_name

class MyClass (object):
name = getCodeName() + '!'

What's the advantage over MyClass.__name_ _?

--
Gabriel Genellina

>>>class C(object):

... name = C.__name__
...
Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "<stdin>", line 2, in C
NameError: name 'C' is not defined

>>>>

I were asking, why do you want a "name" attribute since "__name__" already
exists and has the needed information. And worst, using an internal
implementation function to do such task.

--
Gabriel Genellina