nested class problem

[Stephane Ninin]

Hello all,

I am trying to play with nested class in a script I am making,
and I am not sure I really understand how they work.


Here is some code:

__all__ = ["ITest"]

from exceptions import Exception

class ITest(object):


def __init__(self):
if (self.__class__ == ITest):
raise Exception("ITes t cannot be instanciated")

def read(self,filen ame):
self.__filename = filename

def _getFilename(se lf):
return self.__filename

def make_reader():
return _PTest()
make_reader = staticmethod(ma ke_reader)



class _PTest(ITest):

class _PHandler(objec t):

def __init__(self):
super(_PHandler ,self).__init__ ()
#self.__map={}

def test(self):
pass

def __init__(self):
super(_PTest,se lf).__init__()


def read(self,filen ame):
super(_PTest,se lf).read(filena me)
print "HERE"
print dir()
print dir(self)
print self.__class__
print dir(self.__clas s__)
dh = self._PHandler( )
#dh.test()

if __name__=='__ma in__':

a=ITest.make_re ader()
print dir(a)
b=a.read("")
print b




I want to put class _PHandler in _Ptest,
and use _PHandler in _Ptest methods,
but anything I try doesnot work...

On this configuration, I have:
Traceback (most recent call last):
File "./test.py", line 58, in ?
b=a.read("")
File "./test.py", line 51, in read
dh = self._PHandler( )
File "./test.py", line 34, in __init__
super(_PHandler ,self).__init__ ()
NameError: global name '_PHandler' is not defined

and I have similar problems if I try to access _PHandler
in different ways...
Is this possible somehow ? Or what is the problem with my approach ?
I know I could just dont use nested classes.., but I'd like to try.

Thanks in advance.

Regards,






--
Stephane Ninin

[Peter Otten]

Re: nested class problem

Stephane Ninin wrote:
[color=blue]
> I am trying to play with nested class in a script I am making,
> and I am not sure I really understand how they work.[/color]

[..][color=blue]
>
> class _PTest(ITest):
>
> class _PHandler(objec t):
>
> def __init__(self):
> super(_PHandler ,self).__init__ ()[/color]

Make that
super(_PTest._P Handler, self).__init__( )

or, even better, omit it entirely. Python class hierarchies tend to remain
flat, because inheritance is only necessary for code reuse, not to indicate
a particular interface.
[color=blue]
> #self.__map={}
>
> def test(self):
> pass
>
> def __init__(self):
> super(_PTest,se lf).__init__()
>
>
> def read(self,filen ame):
> super(_PTest,se lf).read(filena me)
> print "HERE"
> print dir()
> print dir(self)
> print self.__class__
> print dir(self.__clas s__)
> dh = self._PHandler( )
> #dh.test()
>
> if __name__=='__ma in__':
>
> a=ITest.make_re ader()
> print dir(a)
> b=a.read("")
> print b
>
>
>
>
> I want to put class _PHandler in _Ptest,
> and use _PHandler in _Ptest methods,
> but anything I try doesnot work...[/color]

I think that's you fighting against the language and - a rare case - python
fighting back :-)
[color=blue]
>
> On this configuration, I have:
> Traceback (most recent call last):
> File "./test.py", line 58, in ?
> b=a.read("")
> File "./test.py", line 51, in read
> dh = self._PHandler( )
> File "./test.py", line 34, in __init__
> super(_PHandler ,self).__init__ ()
> NameError: global name '_PHandler' is not defined
>
> and I have similar problems if I try to access _PHandler
> in different ways...
> Is this possible somehow ? Or what is the problem with my approach ?
> I know I could just dont use nested classes.., but I'd like to try.[/color]

I fail to see the benefit of nested classes. If you want to bring some
structure into your python application, try packages instead.

Peter