[Python-Dev] Dinamically set __call__ method
alex23
wuwei23 at gmail.com
Wed Nov 5 00:28:43 EST 2014
On 11/04/2014 08:52 AM, Roberto Martínez wrote:
>> I am trying to replace dinamically the __call__ method of an object
>> using setattr.
>> Example:
>>
>> $ cat testcall.py
>> class A:
>> def __init__(self):
>> setattr(self, '__call__', self.newcall)
>>
>> def __call__(self):
>> print("OLD")
>>
>> def newcall(self):
>> print("NEW")
>>
>> a=A()
>> a()
>>
>> I expect to get "NEW" instead of "OLD", but in Python 3.4 I get "OLD".
Given that special methods can only be replaced on the class and not the
instance, you could create a new version of the class within __init__
and assign it to the instance:
class A:
def __init__(self, call_method=None):
if call_method:
methods = {'__call__': call_method}
self.__class__ = type('Custom_A', (A,), )
def __call__(self):
return 'original'
>> a = A()
>> a()
"old"
>> b = A(lambda self: 'new')
>> b()
"new"
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