Example value objects using Python 3.6's typing.NamedTuple functionality

values.py

import typing
import datetime


class Period(typing.NamedTuple):
    """
    Value object representing a period in time
    """
    start_dt: datetime.datetime  # noqa (as flake8 doesn't support this syntax as of v3.3)
    end_dt: datetime.datetime  # noqa

    def __repr__(self) -> str:
        return f"{self.start_dt} - {self.end_dt}"

    # Queries

    def start_date(self) -> datetime.date:
        return self.start_dt.date()

    def end_date(self) -> datetime.date:
        return self.end_dt.date()

    # Factories

    def partition(self, num_partitions):
        """
        Split period into a number of equally sized smaller periods
        """
        seconds_per_partition = int((self.end_dt - self.start_dt).total_seconds() / num_partitions)
        new_periods = []
        boundary = self.start_dt
        for n in range(num_partitions):
            period = self.__class__(
                start_dt=boundary,
                end_dt=boundary + datetime.timedelta(seconds=seconds_per_partition))
            new_periods.append(period)
            boundary = period.end_dt
        return new_periods


class ElectricityConsumption(typing.NamedTuple):
    """
    Value object representing electricity consumption over a period
    """
    # The period that these consumption values correspond to
    period: Period 

    electricity_standard: int = None  # noqa
    electricity_day: int = None  # noqa
    electricity_night: int = None  # noqa