Daniel Nogradi a écrit :
>> I have an issue I think Python could handle. But I do not have the
>> knowledge
>> to do it.
>>
>> Suppose I have a class 'myClass' and instance 'var'. There is function
>> 'myFunc(..)'. I have to add (or bind) somehow the function to the
>> class, or
>> the instance. Any help, info or point of reference is wellcome....
>
> How about this (note the first argument 'self' which is the instance
> itself in the second case):
>
>
>
> def method_for_instance( message ):
> print message
>
> def method_for_class( self, message ):
> print message
>
> class myClass( object ):
> pass
>
> inst = myClass( )
> inst.method = method_for_instance
>
> inst.method( 'hello' )
This won't work as expected:
class Bidule(object):
def __init__(self, name):
self.name = name
def greet(self, who):
print "hello %s, my name is %s" % (who, self.name)
b = Bidule('Bruno')
b.greet = greet
b.greet('Daniel')
=>
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/tmp/python-23258Nq5.py", line 10, in <module>
b.greet('Daniel')
TypeError: greet() takes exactly 2 arguments (1 given)
The point is that Python functions are descriptor objects that, when
looked up, return a (bound or unbound) method object wrapping
themselves. So to attach functions as method *on a per-instance basis*,
you either need to use new.instancemethod (as explained by Alex), or
directly use the descriptor protocol, ie:
b.greet = greet.__get__(b)
b.greet('Daniel')
=> hello Daniel, my name is Bruno
Note that you don't need this to attach a function as method to a class
- the descriptor protocol will then JustWork(tm).
HTH
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