Creating a weekly digest

Say our blog has a lot of people who don't use RSS and prefer mailing lists, which is a large number of users. We need some way to create a list of new posts at the end of every week to increase our site's traffic. To solve this problem, we will create a digest task that will be called by a beat worker at 10 am every Saturday.

First, in tasks.py, let's create our task as follows:

@celery.task(
    bind=True,
    ignore_result=True,
    default_retry_delay=300,
    max_retries=5
)
def digest(self):
    # find the start and end of this week
    year, week = datetime.datetime.now().isocalendar()[0:2]
    date = datetime.date(year, 1, 1)
    if (date.weekday() > 3):
        date = date + datetime.timedelta(days=7 - date.weekday())
    else:
        date = date - datetime.timedelta(days=date.weekday())
    delta = datetime.timedelta(days=(week - 1) * 7)
    start, end = date + delta, date + delta + datetime.timedelta(days=6)

    posts = Post.query.filter...