peewee custom field - define allowed values

Question

Two cases:

1.) I'd like to define an attribute (val) that can take the integers 0, 1, or 2 only.

class Trinary(Model):
    """val should accept the values 0, 1 or 2 only"""
    val = IntegerField()

2.) I'd like to define an attribute (val) that can take specific strings only, for example ["strawberry", "peach", "apple"]

class Fruit(Model):
    """val should accept the values "strawberry", "peach" or "apple" only """
    val = ???

Is is possible to implement such a restriction using peewee?

Thanks for your help!

Muff

Answer 1

The objects IntegerField etc. are classes, and can be subclassed (documentation):

The classes should define db_value to convert from python to database, and python_value for the other way round

class TrinaryField(IntegerField):
        def db_value(self, value):
            if value not in [0,1,2]:
                raise TypeError("Non-trinary digit")
            return super().db_field(value)  # call