Neal Becker
3/10/2010 1:41:00 PM
Simon Brunning wrote:
> On 10 March 2010 13:12, Neal Becker <ndbecker2@gmail.com> wrote:
>> Want to switch __call__ behavior. Why doesn't this work? What is the
>> correct way to write this?
>>
>> class X (object):
>> def __init__(self, i):
>> if i == 0:
>> def __call__ (self):
>> return 0
>> else:
>> def __call_ (self):
>> return 1
>>
>>
>> x = X(0)
>>
>> x()
>> TypeError: 'X' object is not callable
>
> __call__ is in the __init__ method's local namespace - you need to
> bind it to the class's namespace instead:
>
> X.__call__ = __call__
>
> But this probably isn't what you want either, since all instances of X
> will share the same method.
>
> What are you trying to do? In your simple example, you'd be much
> better off with a single __call__ method. But you knew that.
>
Sorry, a bit early in the morning. This works:
class X (object):
def __init__(self, i):
if i == 0:
def F (self):
return 0
else:
def F (self):
return 1
self.F = F
def __call__ (self):
return self.F (self)
Not sure if there is a more elegant (or compact) way to write this.
Could __call__ be defined directly within __init__?
What I'm trying to do is make a callable whose behavior is switched based on
some criteria that will be fixed for all calls. In my example, this will
ultimately be determined by the setting of a command line switch.