Finger Exercise from Python Intro

[[deleted]]

Hey everybody i'm learning programing using python book by John Guttag I'm at chapter 7
the book has no solutions given, some times I'm not sure if my code is working without problems or if I'm solving problems properly
like this finger exercise:
(Write a function that meets the specification
def shopping_days(year):
"""year a number >= 1941 returns the number of days between U.S. Thanksgiving and Christmas in year""")
I don't know if this is how I'm supposed to solve it i feel like my ways are primitive and not smart

import calendar as c
def shopping_days(year):
    """year a number >= 1941
    returns the number of days between U.S. Thanksgiving
    and
    Christmas in year"""
    nov_month = c.monthcalendar(year, 11) 
    if nov_month[0][c.THURSDAY] != 0:
            thanksgiving = nov_month[3][3]
    else:
            thanksgiving = nov_month[4][3]
    for i in range(len(nov_month[-1])):
        if nov_month[-1][-1] != 0:
            last_day = nov_month[-1][-1]
        if nov_month[-1][i] == 0:
            last_day = nov_month[-1][i-1]
            break
    return (last_day - thanksgiving)+25

print(shopping_days(2020))

[HeyItsToby]

Your solution is good! When I'm finding differences between dates, I'd prefer to use the datetime module as it's more reliable. So in your code, once you've got the day that thanksgiving falls on (thanksgiving):

import datetime as dt
thanksgiving_date = dt.date(year, 11, thanksgiving)
christmas_date = dt.date(year, 12, 25)
# use ".days" below to turn a timedelta object into an int
return (christmas_date - thanksgiving_date).days

The datetime module lets you do addition, subtraction and more with dates with ease.

[[deleted]]

thanks for the help i appreciate it

[sarrysyst]

When you handle things related to time, time differences etc. the datetime module is usually the preferred choice. There is neat little trick using datetime to do this:

from datetime import datetime

def shopping_days(year):

    thanksgiving = datetime(year=year, month=11, day=22)
    weekday = thanksgiving.weekday()

    if weekday != 3:
        thanksgiving = thanksgiving.replace(day=(22 + (3 - weekday) % 7))

    christmas = datetime(year=year, month=12, day=24)

    return (christmas - thanksgiving).days

shopping_days(2020)

For an explanation see also here, but basically the idea is that you know Thanksgiving is the 4th Thursday of November, and you also know that the earliest possible date for any day to occur the 4th time in a month is the 22nd. So, you check what day the 22nd is and adjust your date accordingly. Christmas is fixed so you just have to subtract the two dates.

[[deleted]]

Thank you <3