timemerge.py

from datetime import datetime
from typing import List


class DatetimeInterval:
    def __init__(self, start, end):
        self.start = start
        self.end = end

    def __lt__(self, other):
        return (self.start, self.end) < (other.start, other.end)

    def __str__(self):
        return f'{self.start} - {self.end}'


def merge_overlaps(records: List[DatetimeInterval]) -> List[DatetimeInterval]:
    if not records:
        return []

    # Ensure chronolocial order.
    records.sort()

    result = []

    current = DatetimeInterval(records[0].start, records[0].end)
    for record in records:
        if record.start <= current.end:
            current.end = max(current.end, record.end)
        else:
            result.append(current)
            current = DatetimeInterval(record.start, record.end)

    # Don't forget about the last one!
    result.append(current)

    return result


records = [
    # Case 1: Standalone interval.
    DatetimeInterval(datetime.fromisoformat('2021-01-01 11:00'), datetime.fromisoformat('2021-01-01 12:30')),

    # Case 2: Second interval enclosed in first interval.
    DatetimeInterval(datetime.fromisoformat('2021-01-01 10:00'), datetime.fromisoformat('2021-01-01 10:30')),
    DatetimeInterval(datetime.fromisoformat('2021-01-01 10:10'), datetime.fromisoformat('2021-01-01 10:15')),

    # Case 3: Second interval extends first interval.
    DatetimeInterval(datetime.fromisoformat('2021-01-01 14:00'), datetime.fromisoformat('2021-01-01 14:30')),
    DatetimeInterval(datetime.fromisoformat('2021-01-01 14:10'), datetime.fromisoformat('2021-01-01 14:40')),
]

result = merge_overlaps(records)

for record in result:
    print(record)