Re: Something to know about Active Python's inheritance mechanism

[Luke <luke(at)rsp.com.au>]

Hi Bernard and Patrick,

There is another developer here who writes pure Python code (non-XSI 
specific) and he was the one who alerted me to this issue and its solution.

So it would appear that this can certainly happen within the Python 
command shell.
But it is worth noting that it only seems to happen when you use 
multiple inheritance where the base classes are from separate files.

The reason that this seems to fix the issue is that when you use 
multiple inheritance with base classes from different files, the class 
types are not known upon importing the modules and "self" is not 
correctly bound when it is evaluated, so that the constructor is looking 
for a certain type (i.e. a subclass of A or A itself), but since B is 
not yet of a known type the python compiler has a spew about it.  
Calling the _dict_ or _call_ methods seem to not check the type or 
binding of "self" before using it, which seems to get around the issue 
quite nicely.

Oh, and yes, it would appear that this does also happen with the 
new-style classes.

cheers,

Luke

Bernard Lebel wrote:

> It's interesting.
>
> When you you call the __dict__, you lookup the name dictionary of the
> class, and then call the name __init__ from the dictionary. I wonder
> why doing it this way would work but not calling the __init__
> directly. Usually having a name show up in the dictionary means it has
> been assigned (or global declared).
> I believe the __call__ name is there for operator overloading, but
> again I just wonder why this would work instead and not the "normal"
> call. Does this also happens within the Python command line shell?
>
>
> Bernard
>
>  
--
luke emrose
technical director - luke.emrose(at)rsp.com.au
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