doomsday.py

#!/bin/python3
# Doomsday algorithm info: https://en.wikipedia.org/wiki/Doomsday_rule

DOOMSDAY_LEAP= [4, 1, 7, 4, 2, 6, 4, 1, 5, 3, 7, 5]
DOOMSDAY_NOT_LEAP= [3, 7, 7, 4, 2, 6, 4, 1, 5, 3, 7, 5]
WEEK_DAY_NAMES= {
0: "Sunday",
1: "Monday",
2: "Tuesday",
3: "Wednesday",
4: "Thursday",
5: "Friday",
6: "Saturday",
}


defget_week_day(year: int, month: int, day: int) ->str:
"""Returns the week-day name out of a given date.

 >>> get_week_day(2020, 10, 24)
 'Saturday'
 >>> get_week_day(2017, 10, 24)
 'Tuesday'
 >>> get_week_day(2019, 5, 3)
 'Friday'
 >>> get_week_day(1970, 9, 16)
 'Wednesday'
 >>> get_week_day(1870, 8, 13)
 'Saturday'
 >>> get_week_day(2040, 3, 14)
 'Wednesday'

 """
# minimal input check:
assertlen(str(year)) >2, "year should be in YYYY format"
assert1<=month<=12, "month should be between 1 to 12"
assert1<=day<=31, "day should be between 1 to 31"

# Doomsday algorithm:
century=year//100
century_anchor= (5* (century%4) +2) %7
centurian=year%100
centurian_m=centurian%12
dooms_day= (
 (centurian//12) +centurian_m+ (centurian_m//4) +century_anchor
 ) %7
day_anchor= (
DOOMSDAY_NOT_LEAP[month-1]
ifyear%4!=0or (centurian==0andyear%400!=0)
elseDOOMSDAY_LEAP[month-1]
 )
week_day= (dooms_day+day-day_anchor) %7
returnWEEK_DAY_NAMES[week_day]


if__name__=="__main__":
importdoctest

doctest.testmod()