Simplification of stupid model code

[dybber]

I'm working on simplifying the stupid model code, still on my TODO is to simplify stupid12 to stupid16.

Some notes for further simplication of the code i've been through so far:

• perhaps we shouldn't even have and use agents_random() in stupid09 and just use random.shuffle(), when model.agents is converted to a list?
• perhaps stupid08, we shouldn't use a global variable to hold the file handle, but use a model variable?
• would be nice if we could avoid update_current_tile()
• would be nice if Agent.align() was named Agent.center_in_tile() or similar
• perhaps all agents should have a reference to their model, instead of the requirement to pass model into all setup/step functions and into all "action" functions

[JensKanstrupLarsen]

Looks good to me.

• Using random.shuffle() is probably the better solution. I have also submitted a pull-request where it is removed, so it might as well be the only solution.
• I think we can avoid having the user make any call to Agent.update_current_tile() if we just make the model itself call it when it adds an agent though Model.add_agent().
• I actually thought Agent.align() had been renamed in another pull request, but apparently not. I agree that Agent.center_in_tile() or similar is better.
• All agents actually have a reference to their model in Agent.__model (it is set when calling Model.add_agent()), but it might as well just be renamed to Agent.model so we can remove the model-parameter required for the button functions.

[dybber]

From StupidModel 12:

"• The model stopping rule is changed: the model stops after 1000 time steps have been executed or when the number of bugs reaches zero."

Should we keep an iteration-count variable in the model? Currently I'm adding it as a TODO in a comment in stupid12-mortality-reproduction.py

[dybber]

I've been through the rest of the stupid models, trying to simplify everything. There's still some TODOs left (marked in comments). In addition to those TODO's everywhere we open a file, and have the on_close handler, we need to make it conditional on the file actually being open:

def close(model):
    if file_handle:
        file_handle.close()

I've only done that in the last model (stupid16), the same fix could be applied in the rest of the models.

[dybber]

Perhaps some utility functions for working with list of agents would be nice:

• does this list contain an agent of the specified type?
• get all agents of a specified type from a list
• sort by an attribute

Also, it's unintuitive that agents_ordered also removes agents that doesn't have the property. Perhaps it's better either to keep them/add them in the end or to error, that is, first let the user get all agents of a specific type and then call a sort function