Class introspection and dynamically determining function arguments

Mark English Mark.English at liffe.com
Fri Jan 21 11:39:31 CET 2005


> From: "Mark English" <Mark.English at liffe.com>
> 
> I'd like to write a Tkinter app which, given a class, pops up a
> window(s) with fields for each "attribute" of that class. The 
> user could enter values for the attributes and on closing the 
> window would be returned an instance of the class. The actual 
> application I'm interested in writing would either have 
> simple type attributes (int, string, etc.), or attributes 
> using types already defined in a c-extension, although I'd 
> prefer not to restrict the functionality to these requirements.

<------------------------>
From: "Diez B. Roggisch" <deetsNOSPAM at web.de>
> whatfor is it planned?

<------------------------>
From: Nick Coghlan <ncoghlan at iinet.net.au
> If this only has to work for classes created for the purpose
> (rather than for an arbitrary class):
<------------------------>

Although I'm writing it for a specific need with a specific set of
classes, I was asking here to find a more general, robust approach. So
handling an arbitrary class would be preferable.

> This is the only way to go, as python has no attribute declarations as
static compiled languages have
The classes I'm dealing with do have attributes since they're
C-Extension types with attributes provided in the "tp_getset" slot. So
this is one case where I can query the class for attributes without
having to create an instance. Thanks for making me think of that, since
looking in the class's __dict__ pretty much gives me what I want. I'm
not sure that that's something I can rely on though which is exactly the
sort of issue where I'd like to know if there's a right way (e.g. an
existing module) to ask a class for its attributes, without poking
around in __dict__ directly and doing some type checking. I guess in a
way I'm asking for introspection with a greater degree of granularity
than "dir".


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