Xavier Décoret a écrit :
> I would like to know if there is for python's classes an equivalent of
> the operator= that can be overidden.
>
> Let's say I have
> >>> a=A()
> and I want to write
> >>> a=5
> and I want this to change some internal value of a instead of making a
> point to a new object (an int 5)
>
> In other word, I would like to be able to use a=5 instead of a.set(5)
>
> Is that possible?
Thanks anybody for the answers. It confirms what I understood of Python.
What I wanted to do is something like this:
def change(x,v):
x = v
class A(object):
def __init__(self,v):
self.x = v
a = A(3)
print a.x # displays 3
change(a.x,4)
print a.x # still displays 3
It may seem weird, but I ensure there is a reason for doing this. In C++
(the language I am mot familiar with), I could define f to take a
pointer to member function of a class, a pointer and a value and achieve
what I want. In python, I cannot that way becauswe when change(a.x,4) is
executed, a.x is "replaced" by ist value (returned by __getattribute__).
Finally, here is how I hold the situation:
class Handle:
def __init__(self,v):
self.__v = v
def __call__(self):
x = self.__v
while callable(x): x=x()
return x
def set(self,v):
self.__v = v
class HandledProperty(object):
def __init__(self,name=""):
self.name = name
def __get__(self,o,t):
return o.__dict__[self]
def __set__(self,o,v):
o.__dict__[self] = Handle(v)
class A(object):
x = HandledProperty("x")
def __init__(self,v):
self.x = v
def change(x,v):
x.set(v)
a = A(3)
print a.x() # displays 3 (notice the () in the call)
change(a.x,4)
print a.x() # still displays 4
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