Calculate antenna length

antenna.py

import argparse
import re
from fractions import Fraction

SPEED_OF_LIGHT = 300000000  # meters/second


class Frequency:
    """
    Converts given frequency to Hertz (Hz)
    frequency = Frequency('5.8GHz')
    hz = frequency.hz
    """
    si_multiples = {  # SI multiples of hertz (Hz)
        'hz': 1,
        'dahz': 10 ** 1,
        'hhz': 10 ** 2,
        'khz': 10 ** 3,
        'mhz': 10 ** 6,
        'ghz': 10 ** 9,
        'thz': 10 ** 12,
        'phz': 10 ** 15,
        'ehz': 10 ** 18,
        'zhz': 10 ** 21,
        'yhz': 10 ** 24,
    }

    def __init__(self, frequency: str):
        """
        :param frequency: e.g '915MHz'
        """
        match = re.match(
            rf'(?P<value>\d+(?:\.\d+)?)(?:\s+)?(?P<unit>{"|".join(self.si_multiples)})$',
            frequency,
            flags=re.I
        )
        if not match:
            raise ValueError(frequency)

        try:
            self.value = int(match.group('value'))
        except ValueError:
            self.value = float(match.group('value'))

        self.unit = match.group('unit')

    def __str__(self):
        return f'{self.value}{self.unit}'

    @property
    def hz(self):
        return self.value * self.si_multiples[self.unit.lower()]


class Antenna:
    """
    antenna = Antenna(Frequency('5.8 GHz'), '1/4')
    antenna.length
    """

    def __init__(self, frequency: Frequency, fraction: Fraction):
        self.frequency = frequency
        self.fraction = fraction

    def __str__(self):
        if self.fraction == Fraction(1, 1):
            return f'{self.frequency} Full Wavelength Antenna {self.length}mm'
        return f'{self.frequency} {self.fraction} Wavelength Antenna {self.length}mm'

    @property
    def length(self) -> float:
        """
        Antenna length in millimeters (mm)
        """
        return round(SPEED_OF_LIGHT / self.frequency.hz * self.fraction * 100 * 10, 2)


if __name__ == "__main__":
    parser = argparse.ArgumentParser(description='Calculate antenna length.')
    parser.add_argument(
        'frequency',
        metavar='frequency',
        type=Frequency,
        help='a frequency for antenna length calculation. [e.g. 5.8GHz]'
    )
    parser.add_argument(
        'fraction',
        metavar='fraction',
        nargs='*',
        type=Fraction,
        default=[Fraction(1, x) for x in range(1, 10)],
        help='wavelength fraction affects antenna length and efficiency. [e.g. 1/4]',
    )
    args = parser.parse_args()
    for f in args.fraction:
        antenna = Antenna(args.frequency, f)
        print(antenna)