Python: parses strings as ISO 8601 timedelta (License: CC0)

parse_timedelta.py

from datetime import timedelta
import re
import unittest


def parse_timedelta(delta: str) -> timedelta:
    """Parses the given string as ISO 8601 timedelta"""
    # https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/time/Duration.html#parse(java.lang.CharSequence)
    match = re.compile(
        r"(?P<sign>[-+]?)P"
        r"(?:(?P<days>[-+]?[0-9]+)D)?"
        r"(T"
        r"(?:(?P<hours>[-+]?[0-9]+)H)?"
        r"(?:(?P<minutes>[-+]?[0-9]+)M)?"
        r"(?:(?P<seconds>[-+]?[0-9]+)"
        r"(?:[.,](?P<microseconds>[0-9]{0,9}))?S)?"
        r")?",
        re.IGNORECASE,
    ).match(delta)
    if not match:
        raise ValueError(f"{delta} cannot be parsed as timedelta!")
    sign = -1 if match.group("sign") == "-" else 1
    return sign * timedelta(
        days=float(match.group("days") or "0"),
        hours=float(match.group("hours") or "0"),
        minutes=float(match.group("minutes") or "0"),
        seconds=float(
            (match.group("seconds") or "0") + "." + (match.group("microseconds") or "0")
        ),
    )


class TestTimedelta(unittest.TestCase):
    """Tests parse_timedelta"""

    def test_parse_timedelta(self) -> None:
        """Tests parse_timedelta"""
        self.assertEqual(
            parse_timedelta("PT20.345S"),
            timedelta(seconds=20, microseconds=345000),
        )
        self.assertEqual(parse_timedelta("PT15M"), timedelta(minutes=15))
        self.assertEqual(parse_timedelta("PT10H"), timedelta(hours=10))
        self.assertEqual(parse_timedelta("PT37H"), timedelta(hours=37))
        self.assertEqual(parse_timedelta("P2D"), timedelta(days=2))
        self.assertEqual(
            parse_timedelta("P2DT3H4M"), timedelta(days=2, hours=3, minutes=4)
        )
        self.assertEqual(parse_timedelta("PT-6H3M"), timedelta(hours=-6, minutes=3))
        self.assertEqual(parse_timedelta("-PT6H3M"), timedelta(hours=-6, minutes=-3))
        self.assertEqual(parse_timedelta("-PT-6H+3M"), timedelta(hours=6, minutes=-3))

        self.assertEqual(
            parse_timedelta("P3DT5H8M11.21S"),
            timedelta(days=3, hours=5, minutes=8, seconds=11, microseconds=210000),
        )