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Question

To start, I have a 2 variables to consider: offer_duration and offer_start_day . An offer can start on any day of the week and the duration is variable (between 1 and 7 days).

I am trying to create a list of all the days of the week that the offer ran on. ie if offer start day is on a Thursday and lasts for 3 days, I need a list outputting the following: ['Thursday', 'Friday', 'Saturday'].

So far I have created a dictionary:

day_of_week = {"Monday":0, "Tuesday":1, "Wednesday":2, "Thursday":3, "Friday":4, "Saturday":5, "Sunday":6}

I am trying to iterate through the dictionary starting on the day of the week (ie Thursday) and iterating offer_duration number of times. I have produced the following but do not know how to get to my solution or if using a dictionary for this problem is the correct approach. any help would be appreciated

for key, num in day_of_week.items():
    if num == test_case('2019-06-27').weekday():
        starting_day = num
print(starting_day)

Answer 1

Dictionaries are not ordered, so you are not guaranteed that your day_of_week keys will get iterated over in the right order. A better way to do this is to use the datetime module and timedelta. Like this:

start = datetime.date(2019, 6, 27)
duration = 3  # days
days = [(start + datetime.timedelta(days=n)).strftime('%A') for n in range(duration)]
assert days == ['Thursday', 'Friday', 'Saturday']

Answer 2

To start I would initiate the day_of_week this way instead:

day_of_week = {0: 'Monday', 1: 'Tuesday', 2: 'Wednesday', 3: 'Thursday', 4: 'Friday', 5: 'Saturday', 6: 'Sunday'}

you can achieve this from your current definition like so:

day_of_week = {v:k for k,v in day_of_week.items()}

then

import datetime

my_week_day = datetime.datetime(2019,6,27).weekday()
offer_length = 3

offer_days = [v for k,v in day_of_week.items() if k in [a%7 for a in range(my_week_day,my_week_day + offer_length)]]

print(offer_days)

Output: ['Thursday', 'Friday', 'Saturday']

Or you could use the below to maintain the correct day order

offer_days = []
for a in range(my_week_day,my_week_day + offer_length):
    offer_days.append(day_of_week[a%7])

print(offer_days)

I only imported datetime since I don't know your test_case function.

Answer 3

You can store the days of week in a list and then use a list comprehension:

days_of_week = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday']
number_of_days = 7
date = dt.date(2019, 6, 29)

>>> [days_of_week[n % 7] for n in range(date.weekday(), date.weekday() + number_of_days)]
['Thursday', 'Friday', 'Saturday', 'Sunday', 'Monday', 'Tuesday', 'Wednesday']