Creating dynamic documents in Flask-MongoAlchemy

Question

I'm using Flask-MongoAlchemy for a personal project. I have some .cfg input files that I want to parse and make into mongodb document entries. Unfortunately, the .cfg files are flat and I want to make multiple different documents from each file. I'd like to define the structure I want to use in one place (in a separate .cfg file) and 1) convert the input files into this format while parsing it, and 2) create the MongoAlchemy document classes using this structure. I'm only having troubles with #2, but I am open to alternative implementations that solve both goals.

Here's my input .cfg file. I'd like to make this into multiple mongodb documents.

[foo]
a = val1
b = val2
c = val3
d = val4

Here's documents.cfg that defines the structure. The values are numbers to distinguish types.

[foo]
    [[bar]]
    a = 1
    b = 1
    [[baz]]
    c = 2
    d = 1

Here are the class definitions

class Bar(db.Document):
    # add class attributes from kwargs
    @classmethod
    def init(cls, **kwargs):
        for k, v in kwargs.items():
            if v == 1:
                setattr(cls, k, db.IntField(min_value=0))

class Baz(db.Document):
    # add class attributes from kwargs
    @classmethod
    def init(cls, **kwargs):
        for k, v in kwargs.items():
            if v == 1:
                setattr(cls, k, db.IntField(min_value=0))
            elif v == 2:
                setattr(cls, k, db.StringField())

I parse documents.cfg to create two dicts:

bar_dict = {'a': '1', 'b': '1'}
baz_dict = {'c': '2', 'd': '1'}

I then pass these to the respective init() methods

Bar.init(**bar_dict)
Baz.init(**baz_dict)

This successfully adds the attributes. However, when creating an instance of Bar (or Baz) I get this error.

mongoalchemy.exceptions.ExtraValueException: a

My guess is that this has to do with the fact that the MongoAlchemy fields should be class attributes, not instance attributes. Any help?

Answer 1

class Bar(db.Document):
    config_extra_fields = 'ignore'
    ...

class Baz(db.Document):
    config_extra_fields = 'ignore'
    ...