Class introspection and dynamically determining function arguments

Mark English Mark.English at liffe.com
Thu Jan 20 12:24:12 CET 2005


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.

The only way I can imagine to do this is to create an instance of the
class in question, and then start poking around in its attributes
dictionary (initially just using dir). So firstly, if there is instead a
way to do this without creating an instance I'd be interested.

Secondly, the code won't know exactly how to initialise the class
instance used to determinte the attributes. Do I need to make it a
prerequesite that all instances can be created with no arguments ?
Should I force/allow the user to pass an instance instead of a class ?
Should I be using inspect.getargspec on the class __init__ method and
then a loop with a try and a lot of except clauses, or is there a nicer
way to do this ? Presumably the pickling code knows how do
serialise/deserialise class instances but I'm not sure how I'd use this
without already having a class instance to hand.

Lastly, does such an app already exist ?

Thanks for any help.


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