readme.md

Date Iterator

Have you ever wanted to iterate over the last 10 days? DateIterator provides simple solution for your problem.

Simple usage

from datetime import datetime, timedelta
from date_iterrator import DateIterator

itr = DateIterator(datetime(2019, 1, 1), datetime(2019, 1, 10), timedelta(days=1))
list(itr)
[(datetime.datetime(2019, 1, 1, 0, 0), datetime.datetime(2019, 1, 2, 0, 0)), 
(datetime.datetime(2019, 1, 2, 0, 0), datetime.datetime(2019, 1, 3, 0, 0)), 
(datetime.datetime(2019, 1, 3, 0, 0), datetime.datetime(2019, 1, 4, 0, 0)), 
(datetime.datetime(2019, 1, 4, 0, 0), datetime.datetime(2019, 1, 5, 0, 0)), 
(datetime.datetime(2019, 1, 5, 0, 0), datetime.datetime(2019, 1, 6, 0, 0)), 
(datetime.datetime(2019, 1, 6, 0, 0), datetime.datetime(2019, 1, 7, 0, 0)), 
(datetime.datetime(2019, 1, 7, 0, 0), datetime.datetime(2019, 1, 8, 0, 0)), 
(datetime.datetime(2019, 1, 8, 0, 0), datetime.datetime(2019, 1, 9, 0, 0)), 
(datetime.datetime(2019, 1, 9, 0, 0), datetime.datetime(2019, 1, 10, 0, 0))]

Difference between open and closed iterator

Open and closed iterators are equal in the case when the interval fits exactly n times between from_date and to_date. On the other side when the parameters are as follows:

itr = DateIterator(datetime(2019, 1, 1), datetime(2019, 1, 10, hour=5), timedelta(days=1))

Now there are 5 hours left at the end. An open iterator (passed as argument closed=False) will stop and ignore the 5 additional hours. Checkout the example:

itr = DateIterator(datetime(2019, 1, 1), datetime(2019, 1, 10), timedelta(days=1), closed=False)
list(itr)
[(datetime.datetime(2019, 1, 1, 0, 0), datetime.datetime(2019, 1, 2, 0, 0)), 
...
(datetime.datetime(2019, 1, 9, 0, 0), datetime.datetime(2019, 1, 10, 0, 0))]

Whereas a closed iterator will generate one more iteration and include the remaining 5 hours:

itr = DateIterator(datetime(2019, 1, 1), datetime(2019, 1, 10), timedelta(days=1), closed=True)
list(itr)
[(datetime.datetime(2019, 1, 1, 0, 0), datetime.datetime(2019, 1, 2, 0, 0)), 
...
(datetime.datetime(2019, 1, 9, 0, 0), datetime.datetime(2019, 1, 10, 0, 0)),
(datetime.datetime(2019, 1, 10, 0, 0), datetime.datetime(2019, 1, 11, 0, 0))]

date_iterator.py

from datetime import datetime, timedelta


class DateIterator:

    def __init__(self, from_date: datetime, to_date: datetime, interval: timedelta, closed: bool = True):
        assert (from_date < to_date), 'to_date must be greater than from_date'

        self.from_date = from_date
        self.to_date = to_date
        self.interval = interval
        self.closed = closed

        self.total_times = None
        self.current_position = None
        self._init_iterator()

    def _init_iterator(self):
        self._calculate_total_times()
        self.current_position = 0

    def _calculate_total_times(self):
        self.total_times = (self.to_date - self.from_date) / self.interval
        is_exact_fit = self.total_times.is_integer()
        if not is_exact_fit and self.closed:
            self.total_times += 1
        self.total_times = int(self.total_times)

    def __iter__(self):
        self._init_iterator()
        return self

    def __next__(self):
        if self.current_position >= self.total_times:
            raise StopIteration

        interval_start_date = self.from_date + self.interval * self.current_position
        interval_end_date = interval_start_date + self.interval
        self.current_position += 1

        return interval_start_date, interval_end_date

test_date_iterator.py

from datetime import datetime, timedelta
from unittest import TestCase

from date_iterrator import DateIterator


class TestDateIterator(TestCase):

    def setUp(self) -> None:
        self.from_date = datetime(2019, 1, 1)
        self.to_date = datetime(2019, 1, 2)
        self.interval = timedelta(hours=6)
        self.expected = [(datetime(2019, 1, 1), datetime(2019, 1, 1, 6)),
                    (datetime(2019, 1, 1, 6), datetime(2019, 1, 1, 12)),
                    (datetime(2019, 1, 1, 12), datetime(2019, 1, 1, 18)),
                    (datetime(2019, 1, 1, 18), datetime(2019, 1, 2))]

    def test_iterator_exact_fit(self):
        itr_closed = DateIterator(self.from_date, self.to_date, self.interval, closed=True)
        itr_open = DateIterator(self.from_date, self.to_date, self.interval, closed=False)

        self.assertEqual(list(itr_closed), self.expected)
        self.assertEqual(list(itr_open), self.expected)

    def test_iterator_closed_not_exact_fit(self):
        self.to_date = datetime(2019, 1, 2, 3)
        self.expected.append((datetime(2019, 1, 2), datetime(2019, 1, 2, 6)))

        itr_closed = DateIterator(self.from_date, self.to_date, self.interval, closed=True)

        self.assertEqual(list(itr_closed), self.expected)

    def test_iterator_open_not_exact_fit(self):
        self.to_date = datetime(2019, 1, 2, 3)

        itr_open = DateIterator(self.from_date, self.to_date, self.interval, closed=False)

        self.assertEqual(list(itr_open), self.expected)