Python date and hour ranges for iterating

date-and-hour-ranges-for-iterating.py

# These tests help understand how python generates ranges of dates
# and hours that can be iterated over.

import datetime

def make_date_by_day(days_back):
    now = datetime.datetime.utcnow()
    at_9am = datetime.datetime(now.year, now.month, now.day, 9, 0,0,0)
    back_then = at_9am - datetime.timedelta(days=abs(days_back))
    return back_then

# Create a range of days
def create_a_range_of_days(): 
    print("Running test function 'create_a_range_of_days'...")
    days_back = 7
    DATE_RANGE_STOP = 0
    DATE_RANGE_STEP = -1
    days = range(days_back, DATE_RANGE_STOP, DATE_RANGE_STEP)
    for day in days:
        start_date = make_date_by_day(day)
        end_date = make_date_by_day(day - 1)
        print(f"Day {day} from {start_date} to {end_date}")

def make_date_by_hour(hours_back):
    now = datetime.datetime.utcnow()
    at_whole_hour = datetime.datetime(now.year, now.month, now.day, now.hour, 0,0,0)
    back_then = at_whole_hour - datetime.timedelta(hours=abs(hours_back))
    return back_then

# Create a range of hours
def create_a_range_of_hours():
    print("Running test function 'create_a_range_of_hours'...")
    days_back = 2
    HOUR_RANGE_STOP = 0
    HOUR_RANGE_STEP = -1
    HOURS_PER_DAY = 24
    hours = range(days_back * HOURS_PER_DAY, HOUR_RANGE_STOP, HOUR_RANGE_STEP)
    for hour in hours:
        start_hour = make_date_by_hour(hour)
        end_hour = make_date_by_hour(hour - 1)
        print(f"Hour {hour} from {start_hour} to {end_hour}")
        

def main():
    print("Running tests...")
    create_a_range_of_days()
    create_a_range_of_hours()

if __name__ == "__main__":
    main()

Using Python 3.8. These functions are used live with one of my clients.