marekw2143 wrote:
> Hi,
>
> I have one class (A) that has defined method createVars. I would like
> to add that method to class B
> The code looks like this:
>
>
> class A(object):
> def createVars(self):
> self.v1 = 1
> self.v2 = 3
> pass
>
> class B(object):
> pass
>
>
> I don't want to use inheritance (because class A has many methods
> defined that class B doesn't need).
You can move createVars() into a mixin or common base class:
class M(object):
def createVars(self): ...
class A(M):
...
class B(M)
...
> When I try the folloowing:
>
>
> B.createVars = C.createVars
> B().createVars()
>
>
> then the following error occurs:
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> TypeError: unbound method createVars() must be called with A instance
> as first argument (got nothing instead)
>
> When I try to add the createVars method to instance of B:
>
>>>> b=B()
>>>> b.createVars = new.instancemethod(A.createVars, b, B)
>>>> b.createVars
> <bound method B.createVars of <__main__.B object at 0x7f6330cc4a90>>
>>>> b.createVars()
>
>
>
> Then the following error raises:
>
>
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> TypeError: unbound method createVars() must be called with A instance
> as first argument (got B instance instead)
>
>
>
> How can I solve this problem?
>>> class A(object):
... def create_vars(self):
... self.x = 42
...
>>> class B(object): pass
...
>>> B.create_vars = A.create_vars.im_func
>>> b = B()
>>> b.create_vars()
>>> b.x
42
An alternative I find a bit cleaner:
>>> def create_vars(self): self.x = 42
...
>>> class A(object):
... create_vars = create_vars
...
>>> class B(object):
... create_vars = create_vars
...
>>> b = B()
>>> b.create_vars()
>>> b.x
42
Peter
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