Django ignore extra arguments on constructing model

Question

I have a small Django project where I get some information from an external source and use it to construct a model instance. The problem is that the source returns a lot (and I mean a lot!) of extra information which I don't need.

At the moment I am having to work out which extra records are in there and manually go through and delete each one. But this isn't very good because

1. It makes for very ugly code and

2. If the external source changes, e.g. it adds a new field, my code will throw an error when I construct a model

   myModel = MyModel(**argDict)
   

Is there a way I can pass an over-complete argDict to my model and have it suppress any errors about extra information and just discard it? I was thinking that I could use a pre_init signal but then I still didn't know how stop that error being given back.

Answer 1

The meta API provides a list of all available field instances via get_fields(). You could write a utility function to filter kwargs for the init:

def init_kwargs(model, arg_dict):
    model_fields = [f.name for f in model._meta.get_fields()]
    return {k: v for k, v in arg_dict.iteritems() if k in model_fields}

then,

kwars = init_kwargs(myModel, arg_dict)
myModel = MyModel(**kwargs)

will work for all models.