Passing an object through COM which acts like str but isn't

[Rafe]

On Aug 15, 10:27 pm, Wolfgang Grafen <wolfgang.gra... at ericsson.com>
wrote:
> Rafe schrieb:
>
> > Forgive me if I mangle any terminology here, but please correct me if
> > I do...
>
> > I have an object which acts exactly like a string as long as I stay in
> > Python land. However, I am using the object in Softimage|XSI, a 3D
> > application on Windows. I'm getting variant erros when trying to use
> > my instances as I would a string.
>
> > XSI was created while (briefly) owned by Microsoft, so knowledge of
> > COM with excel, or anything else, should be applicable I should think.
> > I should also say I am a COM novice and still learning the depths of
> > Python.
>
> > Here is an example...
>
> > class StrLike(object):
> >     def __init__(self, s): self.__data = s
> >     def __repr__(self): return repr(self.__data)
> >     def __cmp__(self, string): return cmp(self.__data, string)
> >     def __contains__(self, char): return char in self.__data
>
> >     __data = ""
> >     def __Set(self, value): self.__data = value
> >     def __Get(self): return self.__data
> >     data = property(fget = __Get,
> >                     fset = __Set,
> >                     fdel = None,
> >                     doc  = "string-like example")
>
> >>>> s = StrLike("test")
> >>>> s
> > 'test'
> >>>> if s == "test": print "cmp works"
> > cmp works
>
> > Now if I try to pass this as I would a string, roughly like so...
> >>>> s = StrLike("test")
> >>>> Application.AnObject.attribute = "test" # works fine
> >>>> Application.AnObject.attribute = s
> > ERROR : Traceback (most recent call last):
> >   File "<Script Block >", line 18, in <module>
> >     XSI.Selection[0].name = s
> >   File "C:\Python25\Lib\site-packages\win32com\client\dynamic.py",
> > line 544, in __setattr__
> >     self._oleobj_.Invoke(entry.dispid, 0, invoke_type, 0, value)
> > TypeError: Objects of type 'StrLike' can not be converted to a COM
> > VARIANT
>
> > Inheriting the str type doesn't raise any errors, but it's immutible
> > so it won't work. The attribute I am trying to set in XSI only takes a
> > string. So is it possible to make a string like object work like a
> > string in this scenario? Is there some built-in method I am missing or
> > some win32com.client trick? Help?
>
> > Thanks for reading,
>
> > - Rafe
>
> Add
> def __str__(self): return repr(self.__data)
>
> then
>  >>> Application.AnObject.attribute = str(s)
> should work
>
> untested
>
> Best Regards
>
> Wolfgang

Thanks for the reply.

I don't need __str__ because Python will automatically use __repr__
when __str__ isn't defined anyway. I also don't want people to have to
wrap this in str().

While str() does work, the real problem is usability. The user will
have to try it, decrypt the "can not be converted" error message and
then figure out on their own that they have to use str(). It will be
intuitive/expected to work especially when used within the context of
the XSI(application) SDK.

Surely there is a way to get my object to be == a string in the eyes
of COM.

- Rafe