Demostración casos de uso de `PEP 484 -- Type Hints`

pep484_use_case.py

import datetime as dt
from collections import OrderedDict as odict
import inspect
import types

from rest_framework import serializers


def function(a: int, b: str):
    pass


def serializer_factory(fn):
    # Class namespace
    cls_name = '{}Serializer'.format(fn.__name__.capitalize())
    cls_dict = odict()

    for param in inspect.signature(fn).parameters.values():
       # Alias
        field_name = param.name
        type_ = param.annotation

        # Build serializer field arguments
        args = {}

        if issubclass(type_, str):
            field_type = serializers.CharField
            args['allow_blank'] = True  # Every CharFiled could be an empty string
        elif issubclass(type_, dt.datetime):
            field_type = serializers.DateTimeField
        elif issubclass(type_, dt.date):
            field_type = serializers.DateField
        elif issubclass(type_, int):
            field_type = serializers.IntegerField
        elif issubclass(type_, dict):
            field_type = serializers.DictField
        elif issubclass(type_, Decimal):
            field_type = serializers.DecimalField
            args.update({'max_digits': 15, 'decimal_places': 4})
        else:
            raise LookupError(
                'Mapping of type {type} not found for field {field!r}'
                ''.format(field=field_name, type=type_)
            )

        # Add field to class namespace
        cls_dict[field_name] = field_type(**args)

    # Create serializer programmatically
    cls = types.new_class(
        cls_name,
        (serializers.Serializer, ),
        {},
        exec_body=lambda ns: ns.update(cls_dict)
    )

    return cls


if __name__ == '__main__':
    FunctionSerializer =  serializer_factory(function)
    assert len(FunctionSerializer().fields) == 2