[Tutor] is it possible to create and amend classes during run-time?

Prasad, Ramit ramit.prasad at jpmorgan.com
Wed May 2 22:56:10 CEST 2012

> >
> > Does anyone know if it is possible during run-time to:
> > a) add attributes to classes, which will unknown at program start, but
> > "emerge" later whilst the program is running?
> > b) add subclasses to class (also during runtime)
> As far as I understand your questions, the answer to both of those is
> yes.  It might help for you to provide an example of exactly what you
> mean, though.
> Here's a quick examples (python 2.6, from the interactive interpreter)
> of adding an attribute to an existing class:
> >>> class Foo(object):
> 	pass
> >>> my_foo = Foo()
> >>> Foo.bar = True
> >>> print my_foo.bar
> True
> >>>
> I defined the class Foo, created an instance of that class, then later
> added an attribute to the class itself.  As you'd expect, that
> attribute is also visible on the instance.
> You second question is a little more difficult to understand.  Classes
> don't know about their subclasses, so you wouldn't normally "add a
> subclass to a class".  Perhaps if you describe what you're trying to
> accomplish, it would be easier to demonstrate how to do it.

Typically unless you need it to be shared across instances (like 
a singleton pattern) you would probably add it to the instance 
instead of the class. So the first answer is Yes.

Like Jerry, I am not sure what you mean by adding a subclass. 
Rather than misinterpret I will just wait for you to clarify.


Ramit Prasad | JPMorgan Chase Investment Bank | Currencies Technology
712 Main Street | Houston, TX 77002
work phone: 713 - 216 - 5423


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