clp2 at rebertia
Aug 4, 2012, 8:31 AM
Post #2 of 2
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On Sat, Aug 4, 2012 at 7:48 AM, vijay shanker <vshanker.88 [at] gmail> wrote:
> hi
> i have this class book
>
> class book:
> def __init__(self,name,price):
> self.name = name
> self.price = price
>
> def __getattr__(self,attr):
> if attr == '__str__':
> print 'intercepting in-built method call '
> return '%s:%s' %
> (object.__getattribute__(self,'name'),object.__getattribute___(self,'price'))
> else:
> return self.__dict__[attr]
>
>>>>b = book('the tempest',234)
>>>>b
> Traceback (most recent call last):
> File "<console>", line 1, in <module>
> File "<console>", line 11, in __getattr__
> KeyError: '__repr__'
>
> i am missing on a concept here. please enlighten me.
A. You ought to be subclassing the `object` class so that your class
is new-style (see
http://docs.python.org/reference/datamodel.html#new-style-and-classic-classes
); "classic" classes are deprecated. Incidentally, you can't intercept
special method lookups on new-style classes like you do in your code
snippet (see http://docs.python.org/reference/datamodel.html#special-method-lookup-for-new-style-classes
). You'll need to define actual __repr__() and/or __str__() methods.
B. The interactive interpreter uses repr(), rather than str(), to
stringify results.
$ python
Python 2.7.2 (default, Jun 20 2012, 16:23:33)
>>> class Foo(object):
... def __str__(self): return "bar"
... def __repr__(self): return "qux"
...
>>> Foo()
qux
>>>
See http://docs.python.org/reference/datamodel.html#object.__repr__
Cheers,
Chris
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