How to validate namedtuple values?

Question

I had namedtuple variable which represents version of application (its number and type). But i want and some restriction to values:

Version = namedtuple("Version", ["app_type", "number"])
version = Version("desktop") # i want only "desktop" and "web" are valid app types
version = Version("deskpop") # i want to protect from such mistakes

My solution for now is primitive class with no methods:

class Version:
    def __init__(self, app_type, number):
        assert app_type in ('desktop', 'web')

        self.app_type = app_type
        self.number = number

Is it pythonic? Is it overkill?

Answer 1

You could use enum.Enum, and typing.NamedTuple instead of collections.namedtuple:

Maybe something like this:

from typing import NamedTuple
import enum

class AppType(enum.Enum):
    desktop = 0
    web = 1

class Version(NamedTuple):
    app: AppType


v0 = Version(app=AppType.desktop)
v1 = Version(app=AppType.web)

print(v0, v1)

output:

Version(app=<AppType.desktop: 0>) Version(app=<AppType.web: 1>)

A undefined AppType raises an AttributeError:

v2 = Version(app=AppType.deskpoop)

output:

AttributeError: deskpoop