singledispatch_example.py

import unittest
from functools import singledispatch


class TestClass1(object):
    @property
    def test_prop(self):
        return "tc1"


class TestClass2(object):
    @property
    def test_prop(self):
        return "tc2"


class TestClass3(object):
    @property
    def test_prop(self):
        return "tc3"


@singledispatch
def build(obj: object) -> object:
    raise NotImplementedError()


@build.register(TestClass1)
def _(obj: TestClass1) -> object:
    return obj.test_prop


@build.register(TestClass2)
def _(obj: TestClass2) -> object:
    return obj.test_prop


class TestSingleDisplatch(unittest.TestCase):
    def setUp(self):
        self.tc1 = TestClass1()
        self.tc2 = TestClass2()
        self.tc3 = TestClass3()

    def test_init(self):
        self.assertEqual(
            build(self.tc1), "tc1"
        )

        self.assertEqual(
            build(self.tc2), "tc2"
        )

        with self.assertRaises(NotImplementedError):
            build(self.tc3)


if __name__ == '__main__':
    unittest.main()