c james <[EMAIL PROTECTED]> writes:
>> class YesNo(object):
>> def __init__(self, which):
>> self.which = which
>>
>> def __call__(self, val):
>> return (self.no, self.yes)[self.which](val)
>>
>> def yes(self, val):
>> print 'Yes', val
>>
>> def no(self, val):
>> print 'No', val
>
> Thanks, I was trying to eliminate another level of indirection with a
> test at each invocation of __call__
Allowing instance lookup of __call__ would slow down normal uses of
the internal __call__ mechanism. Since it used for all function and
method calls, it needs to remain extremely fast. If you're really
worried about performance, you can define YesNo.__new__ to return
either a Yes instance or a No instance, depending on the value:
class YesNo(object):
def __new__(cls, which):
if which:
return object.__new__(Yes)
else:
return object.__new__(No)
def yes(self, val):
print 'Yes', val
def no(self, val):
print 'No', val
class Yes(YesNo):
def __call__(self, val):
self.yes(val) # no check at every call
class No(YesNo):
def __call__(self, val):
self.no(val) # likewise
>>> x = YesNo(True)
>>> x
<__main__.Yes object at 0xb7d0ee8c>
>>> x('foo')
Yes foo
>>> y = YesNo(False)
>>> y
<__main__.No object at 0xb7d0eeec>
>>> y('foo')
No foo
>>> isinstance(x, YesNo)
True
>>> isinstance(y, YesNo)
True
--
http://mail.python.org/mailman/listinfo/python-list
