[Tutor] Accessing class instances

Steve George stevege at i-way.net.uk
Wed Mar 17 06:40:18 EST 2004


I'm having a bit of a problem understanding how to use modules and 
class instances.

The basic idea in my program is to have a number of classes as follows:

	"" Does all my start-up stuff and controls it """

	""" parses options and stores them as attributes"""

	""" Loads a data file and allows operations on it """

I put MainProgram() and Options() classes into one single text file and 
my DataLoader() class into another.

When I instantiate my DataLoader object I want it to look at the 
instance of my Options() class and pull some information from it.  At 
the moment I get:

in get_price
     print Opts.line_size
NameError: global name 'Opts' is not defined

I think I have two problems going on:

a.  I don't think I understand how a class can query an instance of a 
So here my DataLoader class when it's instantiated needs to query an 
instance of my Options() class named Opts.

At the moment I understand how one module can access another and 
instantiate an object e.g. DataLoader.dataloader() but I'm less clear 
how a module can access the instance of that class at runtime.

b.  Have I mis-used modules?
I used the different files/modules thinking that it logically separated 
how I was thinking about the problem.  Howerver, there is some 
information I need to pass back and forward between them, the use of 
'options' is a good example.  How do Python programmers normally get 
around this?

Hope I've been clear in my explanation!



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