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]

Re: Getting a class name

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]

Re: Getting a class name

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]

Re: Getting a class name

En Sun, 18 Feb 2007 04:20:33 -0300, goodwolf <Robert.Katic@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]

Re: Getting a class name

On Feb 17, 8:33 pm, deelan <g...@zzz.itwro 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]

Re: Getting a class name

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

>On Feb 17, 8:33 pm, deelan <g...@zzz.itwro 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]

Re: Getting a class name

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]

Re: Getting a class name

On Feb 18, 1:22 pm, "Michele Simionato" <michele.simion ...@gmail.com>
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]

Re: Getting a class name

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]

Re: Getting a class name

En Sun, 18 Feb 2007 14:14:41 -0300, goodwolf <Robert.Katic@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

[Bruno Desthuilliers]

Re: Getting a class name

Gabriel Genellina a écrit :

En Sun, 18 Feb 2007 14:14:41 -0300, goodwolf <Robert.Katic@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.
>

This might be useful to avoid metaclass hacks when trying to initialize
a class attribute that would require the class name. (my 2 cents)

[Fuzzyman]

Re: Getting a class name

On Feb 18, 11:54 pm, Bruno Desthuilliers
<bdesth.quelque ch...@free.quel quepart.frwrote :

Gabriel Genellina a écrit :
>

En Sun, 18 Feb 2007 14:14:41 -0300, goodwolf <Robert.Ka...@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.

>
This might be useful to avoid metaclass hacks when trying to initialize
a class attribute that would require the class name. (my 2 cents)

It's still an ugly hack. :-)

(But a nice implementation detail to know about none-the-less.)

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

[Gabriel Genellina]

Re: Getting a class name

En Sun, 18 Feb 2007 20:56:48 -0300, Fuzzyman <fuzzyman@gmail .comescribió:

[somebody] wrote:

>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_ _?
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.

>>
>This might be useful to avoid metaclass hacks when trying to initialize
>a class attribute that would require the class name. (my 2 cents)

>
It's still an ugly hack. :-)
(But a nice implementation detail to know about none-the-less.)

Having class decorators would be nice...

--
Gabriel Genellina

[Fuzzyman]

Re: Getting a class name

On Feb 19, 5:11 am, "Gabriel Genellina" <gagsl...@yahoo .com.arwrote:

En Sun, 18 Feb 2007 20:56:48 -0300, Fuzzyman <fuzzy...@gmail .comescribió:
>
>
>

[somebody] wrote:

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_ _?
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.

>

This might be useful to avoid metaclass hacks when trying to initialize
a class attribute that would require the class name. (my 2 cents)

>

It's still an ugly hack. :-)
(But a nice implementation detail to know about none-the-less.)

>
Having class decorators would be nice...
>

Yes - and Guido said he wouldn't be opposed to the idea when it was
poitned out that they would be very useful for both IronPython and
Jython to implement features of their underlying platforms.

I haven't heard anyone (other than you) mention them recently
though...

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

--
Gabriel Genellina

[Gabriel Genellina]

Re: Getting a class name

En Mon, 19 Feb 2007 17:25:56 -0300, Fuzzyman <fuzzyman@gmail .comescribió:

On Feb 19, 5:11 am, "Gabriel Genellina" <gagsl...@yahoo .com.arwrote:

>En Sun, 18 Feb 2007 20:56:48 -0300, Fuzzyman <fuzzy...@gmail .com>
>escribió:

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

>>

>This might be useful to avoid metaclass hacks when trying to

>initialize

>a class attribute that would require the class name. (my 2 cents)

>>

It's still an ugly hack. :-)
(But a nice implementation detail to know about none-the-less.)

>>
>Having class decorators would be nice...

>
Yes - and Guido said he wouldn't be opposed to the idea when it was
poitned out that they would be very useful for both IronPython and
Jython to implement features of their underlying platforms.
>
I haven't heard anyone (other than you) mention them recently
though...

Maybe it's a sign that actually nobody cares about class decorators :(

--
Gabriel Genellina