Get # of days that overlap between two ranges. Usually use this to check if a date range falls within another, larger date range but might as well check for any overlap.

date_range_overlap.py

from datetime import datetime
from collections import namedtuple

Range = namedtuple('Range', ['start', 'end'])

# Returns a positive number of days overlapping, otherwise, returns 0
def get_days_overlap(r1: Range, r2: Range) -> int:
    latest_start = max(r1.start, r2.start)
    earliest_end = min(r1.end, r2.end)

    delta = (earliest_end - latest_start).days + 1
    overlap = max(0, delta)

    return overlap


if __name__ == '__main__':
    def __assert_no_overlaps_for_months_apart():
        assert 0 == get_days_overlap(
            Range(start=datetime(2022, 9, 1), end=datetime(2022, 9, 30)),
            Range(start=datetime(2022, 12, 1), end=datetime(2022, 12, 31))
        )

    def __assert_no_overlaps_for_adjacent_months():
        assert 0 == get_days_overlap(
            Range(start=datetime(2022, 9, 1), end=datetime(2022, 9, 30)),
            Range(start=datetime(2022, 10, 1), end=datetime(2022, 10, 31))
        )

    def __assert_same_range_overlaps():
        assert 30 == get_days_overlap(
            Range(start=datetime(2022, 9, 1), end=datetime(2022, 9, 30)),
            Range(start=datetime(2022, 9, 1), end=datetime(2022, 9, 30))
        )

    def __assert_days_overlap_a_day():
        assert 1 == get_days_overlap(
            Range(start=datetime(2022, 9, 1), end=datetime(2022, 9, 30)),
            Range(start=datetime(2022, 9, 30), end=datetime(2022, 10, 5))
        )

    def __assert_days_overlap_for_range_within_range():
        assert 7 == get_days_overlap(
            Range(start=datetime(2022, 9, 1), end=datetime(2022, 9, 30)),
            Range(start=datetime(2022, 9, 11), end=datetime(2022, 9, 17))
        )

    __assert_no_overlaps_for_months_apart()
    __assert_no_overlaps_for_adjacent_months()
    __assert_same_range_overlaps()
    __assert_days_overlap_a_day()
    __assert_days_overlap_for_range_within_range()

    print('Works fine')

Pretty much this: https://stackoverflow.com/questions/9044084/efficient-date-range-overlap-calculation