Unexpected __metaclass__ method behavior

[anne . nospam01]

Dear fellow Pythonians,

I just stumbled upon the following unexpected behavior:

class TestType(type):
def Foo(self): return 'TestType Foo'
class Test(object):
__metaclass__ = TestType
def Foo(self): return 'Test Foo'
t = Test()
print t.Foo()
print Test.Foo()

This will produce:
Test Foo
Traceback (most recent call last):
  File "test.py", line 8, in 
print Test.Foo()
TypeError: unbound method Foo() must be called with Test instance as
first argument (got nothing instead)

I can imagine why this is happening, and that there is no easy
solution, but it is not what I was expecting.

Anybody willing to explain the details of what's exactly going on
during the method lookup of Test.Foo?

Kind regards,
Sebastian
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Re: Unexpected __metaclass__ method behavior

[anne . nospam01]

Well, you see, I have some database functions that deal with "things"
which are either classes or instances thereof. I though polymorphism
would be a nice way to handle them identically, like:

def do(thing): thing.Foo()
do(t)
do(Test)

But never mind, I now understand that Test.__dict__ can contain only
one entry for 'Foo', and that this must be matched.

Kind regards,
Sebastian
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What is the encoding of __file__?

[anne . nospam01]

Dear all,

can someone quickly tell me what the encoding of __file__ is? I can't
find it in the documentation.

BTW, I'm using Python 2.5.1 on WIndows XP and Vista.

Kind regards,
Sebastian
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Re: What is the encoding of __file__?

[anne . nospam01]

On 7 Jan., 23:06, "Martin v. Löwis" <[EMAIL PROTECTED]> wrote:
> > can someone quickly tell me what the encoding of __file__ is? I can't
> > find it in the documentation.
>
> > BTW, I'm using Python 2.5.1 on WIndows XP and Vista.
>
> It's platform-specific - the same encoding that is used for file names
> (i.e. sys.getfilesystemencoding()). On Windows, it will be "mbcs", which
> in turn is installation-specific - on Western European/US installations,
> it's "windows-1252".

Thanks, I'll then use sys.getfilesystemencoding() to decode _file__
and re-encode into utf-8, which is the default encoding of all strings
in our software, as we deal a bit with Chinese terms.

Windows-1252 on my box. I just created a directory containing Chinese
characters (on Vista), and whoa, files opened with IDLE are empty,
import doesn't find modules in that directory. Of course Windows-1252
can't encode these ...

But I understand that Python 3 will clean this up?

Kind regards,
Sebastian
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Inconsistency of special class method lookup?

[anne . nospam01]

Folks,

I'm running into the following issue. A staticmethod of a class seems
not to be accepted as a special class method of the class object
itself. For example:

class Foo(object):
def __len__(): return 2
__len__ = staticmethod(__len__)
print len(Foo)
>>>
Traceback (most recent call last):
  File "C:/Dokumente und Einstellungen/All Users/Dokumente/foo.py",
line 4, in ?
print len(Foo)
TypeError: len() of unsized object

However, the following works:

class FooType(type):
def __len__(self): return self.l()
class Foo(object):
__metaclass__ = FooType
def l(): return 3
l = staticmethod(l)
print len(Foo)
>>>
3

Any good reason why the lookup process doesn't find __len__ as
staticmethod of the class?

Regards,
Sebastian (posting using the account of my wife)

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Re: Inconsistency of special class method lookup?

[anne . nospam01]

Thanks.

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