Peewee: dynamically set table_name when model is instanced

Question

I am pretty sure this is not a duplicate. I know we can 'dynamically' set the table name using this:

class DBmodel(Model)
    class Meta:
        database = db
        table_name = "foobar"

But what if I want to change table_name every time DBmodel is instanced?

For example consider this working snippet:

#!/usr/bin/env python3
# coding: utf-8

from peewee import *

conf = {
    "foo": {
        "foo1": "CharField(null=True)",
        "foo2": "CharField(null=True)"
    },
    "bar": {
        "bar1": "CharField(null=True)",
        "bar2": "CharField(null=True)"
    }
}

db = SqliteDatabase("foobar.db")


class DBmodel(Model):
    class Meta:
        database = db
        table_name = "foobar"


class Data:
    def __init__(self, conf):
        self.conf = conf
        self.DBmodel = DBmodel()
        for entry in self.conf:
            # I have to use eval because my conf is actually coming from parsed json, where I can only have text field
            self.DBmodel._meta.add_field(entry, eval(self.conf[entry]))


if __name__ == "__main__":
    dataFoo = Data(conf["foo"])
    dataBar = Data(conf["bar"])
    dataFoo.DBmodel.create_table()
    dataBar.DBmodel.create_table()

So I get:

$ sqlite3 foobar.db
SQLite version 3.22.0 2018-01-22 18:45:57
sqlite> .schema foobar
CREATE TABLE IF NOT EXISTS "foobar" ("id" INTEGER NOT NULL PRIMARY KEY, "foo1" VARCHAR(255), "foo2" VARCHAR(255), "bar1" VARCHAR(255), "bar2" VARCHAR(255));

But I want to have two tables like this:

$ sqlite3 foobar.db
SQLite version 3.22.0 2018-01-22 18:45:57
sqlite> .schema foo
CREATE TABLE IF NOT EXISTS "foo" ("id" INTEGER NOT NULL PRIMARY KEY, "foo1" VARCHAR(255), "foo2" VARCHAR(255));
sqlite> .schema bar
CREATE TABLE IF NOT EXISTS "bar" ("id" INTEGER NOT NULL PRIMARY KEY, "bar1" VARCHAR(255), "bar2" VARCHAR(255));

Of course, I could duplicate my DBmodel and change table_name every time, but this seems ugly. Is there a better solution?

Answer 1

You can always declare classes dynamically using the builtin type :

attrs = {
    'foo': TextField(),
    'bar': TextField(),
}
MyModel = type('MyModel', (BaseModel,), attrs)

Why does your "Data" have to be a class? Presumably all you need is a function that accepts a key to the config dict and you would return a new class object. You might want to think about that.

I'll also point out that doing this is a bad idea.

Answer 2

 # coding: utf-8
 from peewee import *
 db = SqliteDatabase("foobar.db")
 def get_table_name(model_class):
     return model_class.__name__

 def class_generator(class_name):
     value_dict = {}
     for i in range(2):
         value_dict['{}{}'.format(class_name, i+1)] = CharField(null=True)
     value_dict['Meta'] = type('Meta', (object, ), {'database': db, 'table_function': get_table_name})
     return type(class_name, (Model, ), value_dict)

 if __name__ == "__main__":
     dataFoo = class_generator("foo")
     dataBar = class_generator("bar")
     dataFoo.create_table()
     dataBar.create_table()

Answer 3

DBmodel._meta.set_table_name(<table_name>)