Get rid of recursive call __getattr__

Peter Hansen peter at engcorp.com
Wed Dec 14 15:56:54 CET 2005


Pelmen wrote:
>>>>class Test:
> 
> 	  def __getattr__(self, attr):
> 	    print attr
> 
> 	  def foo(x):
> 	    print x
> 
> 
>>>>t = Test()
>>>>print t
> 
> __str__
> 
> Traceback (most recent call last):
>   File "<pyshell#23>", line 1, in -toplevel-
>     print t
> TypeError: 'NoneType' object is not callable
> 
> what i have to do? define __str__ explicitly?

Yes.  Or subclass "object" as it has a default __str__ already.

(By the way, you do realize that the NoneType message comes because your 
__getattr__ is returning None, don't you?  So technically you could also 
return a real value (in this case a callable) and it would also work, 
though it's very likely not what you wanted.

class Test:
     def __getattr__(self, name):
         def callable_attribute():
             return 'i am attr %s' % name
         return callable_attribute

 >>> t = Test()
 >>> print t
i am attr __str__

-Peter




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