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Modular python admin pages

I'm building a personal website that I need to apply modularity to it for purpose of learning. What it means is that there is a model that contains x number of classes with variations, as an example a button is a module that you can modify as much depending on provided attributes. I also have a pages model that need to select any of created modules and render it. I can't find any documentation of how to access multiple classes from one field to reference to.
Model structure is as below:
Modules, contains module A and module B
Pages should be able to select any of module A and order its structure.
Please let me know if not clear, this is the simplest form I could describe. Am I confusing this with meta classes? How one to achieve what I'm trying to achieve?

I ended up using Proxy models but will also try polymorphic approach. This is exactly what is designed to do, inherit models from a parent model in both one to many and many to many relationships.

Global Variables in Django Admin Site

This was my original question, but it was not answered and so I thought Id post again with some of the strategies that I have tried, and be a little more specific.
I want to create a dynamic admin site, that based on if the field is blank or not will show that field. So I have a model that has a set number of fields, but for each individual entry will not contain all of the fields in my model and I want to exclude based on if that field is blank. My project is about bridges, and so to put it in practical terms I have a model that has every bridge part in it (this roughly is equivalent to 100), but each individual bridge (mapped to each unique brkey) will not have all 100 bridge parts. And so, I can prepopulate all of the fields it does have, but then the admin site has 100 other fields, and I would like to not display those fields that were not used on my admin site for that specific bridge, but those fields will differ with pretty much every bridge.
Like I said before, I have a unique bridge identifier(a unique 15 digit string), that correlates to each bridge, and then all of the various different variables that describe the bridge.
I have it set up now that the user will go to a url with the unique bridgekey and then this will create an entry of that bridge. So (as i am testing on my local machine) it would be like localhost/home/brkey and that code in my views.py that corresponds to that url is
Is this a final route that I have to take? I am very new to JavaScript and so I do not want to take this route but I will if I have to. Also does Django use Javascript in anyway that is syntactically different? If so I cannot find any Django documentation on incorporating Javascript into my admin site.
A final option that I have exhausted is to use global variables. Instead of having the url that creates the entry in my Views.py, I placed it in my admins.py, and had my modelAdmin class in there as well, so like this.
admins.py
-set up global variable
bridgekey_unique = " "
If I can find a way to either pass that unique bridge key to my modelAdmin class, or figure out if that said field is blank because the bridge doesnt have that part, I will be able to achieve what I want without using Javascript. I have tried a lot of variations of all two of theses strategies to no avail, but have not tried the JavaScript idea as I dont really know any javascript at all.
Sorry for the lengthy post, but people said I wasnt specific enough. Any help would be greatly appreciated.

I didn't read all of that - sorry, there's too much. But I did notice your comment that you expect to access in your modeladmin definition a variable that you set in your view. That can't possibly work.
Anything at class level is always executed when the module containing the class is first imported. That is when the server process starts up, so there is no possible way anything done in the view can have happened yet.
You almost never want to have any logic at class level. You need to put it in methods, which are called at the relevant time. In this case, you probably need to use the get_fields method.
Edit
Looking further up at your attempt at a get_fields method, I can't see at all what you are trying to do here. 'prestressed_concrete_deck' is a literal string, and could never be None, so neither of your conditions can ever be true. And as to your question about what the parameters are, the documentation for that method explains clearly that obj is the object being edited.

Create portfolio backed skill-set in django ORM

I have a specialized User class that inherits from django.contrib.auth.models.User. Now, this User class will have tags associated with it, for example: Blogger, French Cuisine Cook, Python Programmer.
Ideally, what I want to do, is have each of these traits backed up by something that they have done, ideally a PortfolioItem. So, a User will have a set of tags, and these tags, and the relationship with each of these tags is going to be understood through these PortfolioItems. How would one achieve something like this using the django ORM?
Please note, that the tags are generic, however, the portfolios behind each of these tags are unique to every user.
How would one go about doing, this using the through variable in django ORMs.
UPDATE
I've tried simple adding PortfolioItem as the through variable, but in that case you will need to create a unique tag each time you want to add a list of portfolio item. The thing is I want tags to be generic.

In Django, searching and filter by searchbox and categories in one go?

I wonder if you could help me.
I have a list of data that will be displayed on one page. There is a simple search box, a list of categories and a list of tags that can all be used to filter the list of data. I'm trying to built it from the ground up (so it doesn't require JavaScript) but eventually it will submit the search criteria and return back a new list using Ajax.
So I have a list of categories in my database ('large', 'small', etc), and I have a list of tags in my database ('wooden', 'brass'). Tags are used to filter down more of what's in the categories. I then have a search box. Ideally, I want the user to effectively tick which categories they want, tick what tags they want and possibly put a search for keywords, and then submit all of that data so it can be queried and a new list of the filtered data can be returned.
I'm not a Django expert, and I'm stuck on how and where to do this... What is the Django way of spitting out the categories as a checkbox list, the tags as a checkbox list and the search box with a submit button... Which when submitted, I can take all that data and do the necessary queries on the database? I don't quite understand how I'd do this... I've been looking at the Django Docs and the Django Book for a few days and the way I'm doing things doesn't seem to be listed.
Please, any help at all would be fantastic.

spitting out the categories as a checkbox list,
the tags as a checkbox list and the
search box with a submit button...
This is a <form> in your HTML page. It probably doesn't match anything in the Django model very well. It's a unique form built more-or-less manually.
I can take all that data and do the necessary queries on the database?
That's a view function.
You'll probably have something like this.
objects= SomeModel.objects
if request.GET ... has categories ...
objects = objects.filter( ... categories ... )
if request.GET ... has tags ...
objects = objects.filter( ... tags ... )
if request.GET ... has search ...
objects = objects.filter( something__contains( search ) )
return render_to_response( ... etc. ... )
the way I'm doing things doesn't seem to be listed.
You're beyond the tutorial here.
What to do?
Do the ENTIRE tutorial. All the way through. Every step. It doesn't seem like it solves your problem, but you MUST do the ENTIRE tutorial.
Design your model. You didn't mention the model in the question. It's the absolutely most important and fundamental thing.
Create the default admin interface for that model. Get the default admin interface to work and do the kinds of things you'd like to do. It has great search, category and tag filtering.
In order to get the default admin to work, you'll need to design fairly sophisticated model and form features. You'll probably have to add method functions to your model as well as choice items and other goodness.
AFTER you have the admin page pretty close to what you want, you can write you own customized view.
each single checkbox has a different name ('category_option_1', 'category_option_2', etc.) ... How do I read these? I can't just put request.POST['category_option_n']?
Really? Why didn't your question say that?
Are you asking about this?
for k in range(1024):
name = 'category_option_{0}'.format(k)
# Use request.POST.get(name,None) to build a `Q` object

Return template as string - Django

I'm still not sure this is the correct way to go about this, maybe not, but I'll ask anyway. I'd like to re-write wordpress (justification: because I can) albeit more simply myself in Django and I'm looking to be able to configure elements in different ways on the page. So for example I might have:
Blog models
A site update message model
A latest comments model.
Now, for each page on the site I want the user to be able to choose the order of and any items that go on it. In my thought process, this would work something like:
class Page(models.Model)
Slug = models.CharField(max_length=100)
class PageItem(models.Model)
Page = models.ForeignKey(Page)
ItemType = models.CharField(max_length=100) # tells me which model to display
InstanceNum = models.IntegerField() # tells me which instance of which model...
Then, ideally, my template would loop through all the PageItems in a page which is easy enough to do.
But what if my page item is a site update as opposed to a blog post? Basically, I am thinking I'd like to pull different item types back in different orders and display them using the appropriate templates. Now, I thought one way to do this would be to, in views.py, to loop through all of the objects and call the appropriate view function, return a bit of html as a string and then pipe that into the resultant template.
My question is - is this the best way to go about doing things? If so, how do I do it? If not, which way should I be going? I'm pretty new to Django so I'm still learning what it can and can't do, so please bear with me. I've checked SO for dupes and don't think this has been asked before...
I've also looked at Django-cms to see if that helps, but I couldn't get to grips with it.
Any suggestions?

First, some puzzelement.
InstanceNum = models.IntegerField() # all models have primary keys.
In Django, all model are assigned an integer primary key.
The comment doesn't make sense, since you don't need to add a primary key like this. The PageItem already has a primary key.
Also, please use lower case letters for attributes. Only Use Upper Case for Class Names. Please.
"But what if my page item is a site update as opposed to a blog post? Basically, I am thinking I'd like to
pull different item types back in
different orders and display them
using the appropriate templates"
Different types usually means different models. Rather than a vague "PageItem", you probably want to have "Site Update" and "Blog Post" as separate models.
You can then iterate through these various objects and display them in the template.
You can easily have your various Models defined with a method to return HTML information. You don't (generally) want to return fully-baked HTML. But CSS ID or Class information is sometimes helpful.
class SiteUpdate( models.Model ):
page = models.ForeignKey(Page)
item_text = models.CharField(max_length=100)
item_css_class = models.CharField(max_length=64)
Now you can generate this into the template with a simple <div class="{{item.item_css_class}}">{{item.item_text}}</div> and use CSS to handle the formatting details that distinguish site update as opposed to a blog post.

The include template tag can take a variable containing the template to include, so you could loop through a sequence containing the various sub-templates and include them in turn, maybe using a dict to map friendly names to template filenames.