PYTHON 3.8 date range

A Pythonic way to do this is to create an iterator, something like:

from datetime import datetime, timedelta

class dater(object):
    def __init__(self, first, lastPlusOne, inclusiveEnd = False):
        # Store important stuff, adjusting end if you want it inclusive.

        self.__oneDay = timedelta(days = 1)
        self.__curr = datetime.strptime(first, "%Y-%m-%d").date()
        self.__term = datetime.strptime(lastPlusOne, "%Y-%m-%d").date()
        if inclusiveEnd:
            self.__term += self.__oneDay

    def __iter__(self):
        return self

    def __next__(self):
        return self.next()

    def next(self):
        # This is the meat. It checks to see if the generator is
        # exhausted and raises the correct exception if so. If not,
        # it saves the current, calculates the next, stores that
        # for the next time, then returns the saved current.

        if self.__curr >= self.__term:
            raise StopIteration()

        (cur, self.__curr) = (self.__curr, self.__curr + self.__oneDay)
        return cur

You can call it with something like (from your example):

for date in dater("2019-09-21", "2019-10-09", inclusiveEnd=True):
    print(date)

to get:

2019-09-21
2019-09-22
2019-09-23
2019-09-24
2019-09-25
: no need to show it all, trust me :-)
2019-10-08
2019-10-09

The advantage of using an iterator is that:

• the code to use it becomes a very simple for loop, similar to Python’s many other methods; and
• you can make the __init__ constructor arbitrarily complex (for example, accepting datetime or date variables as well as the current strings).

That last point bears some extra explanation. In the code that sets up the self.__curr (for example), you can use something like this:

if type(first) == type(date(2000, 1, 1)):        # copy a date.
    self.__curr = first
elif type(first) == type(datetime(2000, 1, 1)):  # extract date from datetime.
    self.__curr = first.date()
else:                                            # convert string.
    self.__curr = datetime.strptime(first, "%Y-%m-%d").date()

This will detect the source type and adjust behaviour so that you get a date regardless. If you do the same thing for the final date, you’ll get a truly adaptable iterator that can even start and end with different representations:

for mydate in dater("2000-01-01", datetime.now()):
    process_every_date_from_start_of_2000_to_yesterday(mydate)