mildly OT: python class creating a class question

[jonp]

Sorry if this a bit of topic, mods are free to move it to the general discussion section.

I have moderate python scripting skills with just a bit of familiarity with classes, and am currently scripting some pipeline-y stuff at work. We have an established directory structure that follows, more or less, standard conventions (project/sequence/etc). Inspired by the way Houdini turns its own hierarchical structure into objects, I'd like to do something similar with our directory structure. Just as a SOP node object can only be created from within (or by) an OBJ node in Houdini's python implementation, I would like to write a module within which, for example:

- only Sequence classes can be created by, or attached to, a Project class parent

- only an Element class can be created by, or attached to, a Sequence class parent

I only ask here because of my exposure to this kind of python scripting comes directly from Houdini. I've created scripts that have classes creating other classes, but there is no enforcement of scope with each individual class.

If anyone has any pointers to a general coding style that facilitates this I'd be quite grateful.

Cheers,

Jon

[edward]

In your Project.addSequence(sequence) method, can't you just check the type and raise an exception or something?

[jonp]

Hey thanks for replying. Quick question: within my Sequence class, how would I check the type of whatever was initializing it? Like how to know the difference between:

seq = Sequence(path)
seq = proj.create_seq(path)
[/CODE]

I haven't pushed into this as much as I originally planned, since I got halfway down that road and felt like it was far enough for what we were using it for anyways.

[sanostol]

You can add the project as project variable to the sequence for example

class cSequence():
def __init__(self, path, project):
	 self.project = project
	 self.path	 = path

class cProject():
def __init__(self,path):
	 self.path	 = path
	 self.sequences = []

def addSequence(self):
	 sequence = cSequence(self.path, self)
	 self.sequences.append(sequence)


project = cProject("testpath")
project.addSequence()
print project.sequences[0].path
print project.sequences[0].project

[/CODE]

if You strictly stick to class functions You can not create a sequence inside a element, as element has no addSequence function, only the project class has one. so by designing You classes You can enforce consistency. Of cource one can attach a sequence to a element, but than he leaves the designed path

Edited December 14, 2012 by sanostol