Typed namedtuple

typednamedtuple.py

# -*- coding: utf-8 -*-

from collections import namedtuple


def typednamedtuple(typename, field_names, field_types):
    '''Typed namedtuple

    An implementation of typed namedtuple.

    >>> Point = typednamedtuple('Point', ['id', 'x', 'y'], [str, float, float])
    >>> Point.__doc__
    'Point(id: str, x: float, y: float)'
    >>> p = Point('nodeXX', '0.8', '0.5')
    >>> p.id
    'nodeXX'
    >>> p.x + p.y
    1.3
    '''
    ntuple = namedtuple(typename, field_names)
    _tuple_new = ntuple.__new__

    def __new__(cls, *args):
        converted_args = [t(f) for f, t in zip(args, field_types)]
        return _tuple_new(cls, *converted_args)
    ntuple.__new__ = __new__

    arg_list = ', '.join(f'{f}: {t.__name__}' for f, t in zip(field_names, field_types))
    ntuple.__doc__ = f'{typename}({arg_list})'

    return ntuple


if __name__ == '__main__':
    inputs = ['user01', '0.2', '0.4']
    fields = ['user_id', 'x', 'y']
    types = [str, float, float]

    Point = typednamedtuple('Point', fields, types)
    p = Point(*inputs)
    print(p)
    print(p.x + p.y)

    Point2 = namedtuple('Point2', fields)
    converted_inputs = [t(i) for i, t in zip(inputs, types)]
    p = Point2(*converted_inputs)
    print(p)
    print(p.x + p.y)

    from typing import NamedTuple
    class Point3(NamedTuple):
        user_id: str
        x: float
        y: float
    p = Point3(*inputs)
    print(p)
    print(p.x + p.y)