Ah I see. So istead of creating the classes diectly I use a facroty class as a buffer - I tell it what I want and it makes the appropriate instances. I am not enitely sure that applies here though (I may be wrong)
Currently I have: camera_list[] class camera: def __init__(self,alpha,beta,gamma...): self.alpha=alpha self.beta=beta self.gamma=gamma ... for (some conditions) camera_list.append(camera(alpha,beta,gamma...) the append command creates an instance of the camera class and shoves it at the end of a list for each itteration of the loop. However, I want to recover various types of information from the text file I am parsing - not just (as in the example above) camera data. However I am trying to keep the interface the same. so I can have collectSomeData.getData() as well as collectSomeOtherData.getData() In each case the getData impementation will be different to suit the required task. So something like: class camera: def __init__(self,alpha,beta,gamma...): self.alpha=alpha self.beta=beta self.gamma=gamma ... class list_type1 def createList() : for (some conditions) camera_list.append(camera(alpha,beta,gamma...) class list_type2 def createList() : for (some other conditions) camera_list.append(camera(alpha,beta,gamma...) data1=list_type1() data2=list_type2() data1.createList() data2.createList() The only change above is that I have taken the list appending loop and put it into a class of its own. However, wheras when the method list_type_2 was not in a class tings worked fine, when put into a class as above and the method attempts to create an instance of the camera class to append to its list it complains. I'm pretty sure there is a solution, and I think I will kick myself when I work it out (or have it pointed out)! Cheers, Ben -- http://mail.python.org/mailman/listinfo/python-list