croniter get_next and get_prev for cron schedule iteration: working versions (tested 2026-10-16)

croniter==6.2.4
pytest==9.1.1

from datetime import datetime
from itertools import islice

from croniter import croniter

def next_runs(expr: str, start: datetime, count: int = 1, day_or: bool = True) -> list[datetime]:
    it = croniter(expr, start, day_or=day_or)
    return [it.get_next(datetime) for _ in range(count)]

def prev_runs(expr: str, start: datetime, count: int = 1) -> list[datetime]:
    it = croniter(expr, start)
    return [it.get_prev(datetime) for _ in range(count)]

def upcoming(expr: str, start: datetime, count: int) -> list[datetime]:
    # all_next() is an infinite generator: always bound it with islice.
    it = croniter(expr, start)
    return list(islice(it.all_next(datetime), count))

def is_valid(expr: str) -> bool:
    return croniter.is_valid(expr)

from datetime import datetime, timezone

import pytest
from croniter import CroniterBadCronError, croniter

from schedule import is_valid, next_runs, prev_runs, upcoming

def test_next_is_strictly_after_matching_start():
    start = datetime(2024, 1, 1, 0, 0)
    # start already matches the cron, so the next hit is the following day
    assert next_runs("0 0 * * *", start)[0] == datetime(2024, 1, 2)
    assert upcoming("0 0 * * *", start, 3) == [
        datetime(2024, 1, 2),
        datetime(2024, 1, 3),
        datetime(2024, 1, 4),
    ]

def test_prev_walks_backwards():
    start = datetime(2024, 1, 1, 0, 0)
    assert prev_runs("0 0 * * *", start, 2) == [
        datetime(2023, 12, 31),
        datetime(2023, 12, 30),
    ]

def test_default_ret_type_is_epoch_seconds():
    start = datetime(2024, 1, 1, tzinfo=timezone.utc)
    ts = croniter("0 0 * * *", start).get_next()
    assert isinstance(ts, float)
    assert datetime.fromtimestamp(ts, tz=timezone.utc) == datetime(2024, 1, 2, tzinfo=timezone.utc)

def test_day_of_week_seven_equals_sunday():
    start = datetime(2024, 1, 2)
    assert next_runs("0 0 * * 0", start)[0] == next_runs("0 0 * * 7", start)[0] == datetime(2024, 1, 7)

def test_day_or_toggles_or_and_semantics():
    start = datetime(2024, 1, 2)
    # default day_or=True: day-of-month OR day-of-week -> next Monday
    assert next_runs("0 0 1 * 1", start)[0] == datetime(2024, 1, 8)
    # day_or=False: day-of-month AND day-of-week -> first 1st that is a Monday
    assert next_runs("0 0 1 * 1", start, day_or=False)[0] == datetime(2024, 4, 1)

def test_invalid_expression():
    assert is_valid("0 0 * * *") is True
    assert is_valid("61 0 * * *") is False
    with pytest.raises(CroniterBadCronError):
        croniter("61 0 * * *", datetime(2024, 1, 1))

[pytest]
pythonpath = .