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Python/maths/zellers_congruence.py at Upgrade-to-Python-3.8 · hackhit/Python · GitHub

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import datetime

import argparse

def zeller(date_input: str) -> str:

"""

Zellers Congruence Algorithm

Find the day of the week for nearly any Gregorian or Julian calendar date

>>> zeller('01-31-2010')

'Your date 01-31-2010, is a Sunday!'

Validate out of range month

>>> zeller('13-31-2010')

Traceback (most recent call last):

...

ValueError: Month must be between 1 - 12

>>> zeller('.2-31-2010')

Traceback (most recent call last):

...

ValueError: invalid literal for int() with base 10: '.2'

Validate out of range date:

>>> zeller('01-33-2010')

Traceback (most recent call last):

...

ValueError: Date must be between 1 - 31

>>> zeller('01-.4-2010')

Traceback (most recent call last):

...

ValueError: invalid literal for int() with base 10: '.4'

Validate second seperator:

>>> zeller('01-31*2010')

Traceback (most recent call last):

...

ValueError: Date seperator must be '-' or '/'

Validate first seperator:

>>> zeller('01^31-2010')

Traceback (most recent call last):

...

ValueError: Date seperator must be '-' or '/'

Validate out of range year:

>>> zeller('01-31-8999')

Traceback (most recent call last):

...

ValueError: Year out of range. There has to be some sort of limit...right?

Test null input:

>>> zeller()

Traceback (most recent call last):

...

TypeError: zeller() missing 1 required positional argument: 'date_input'

Test length fo date_input:

>>> zeller('')

Traceback (most recent call last):

...

ValueError: Must be 10 characters long

>>> zeller('01-31-19082939')

Traceback (most recent call last):

...

ValueError: Must be 10 characters long

"""

# Days of the week for response

days = {

"0": "Sunday",

"1": "Monday",

"2": "Tuesday",

"3": "Wednesday",

"4": "Thursday",

"5": "Friday",

"6": "Saturday",

}

convert_datetime_days = {0: 1, 1: 2, 2: 3, 3: 4, 4: 5, 5: 6, 6: 0}

# Validate

if not 0 < len(date_input) < 11:

raise ValueError("Must be 10 characters long")

# Get month

m: int = int(date_input[0] + date_input[1])

# Validate

if not 0 < m < 13:

raise ValueError("Month must be between 1 - 12")

sep_1: str = date_input[2]

# Validate

if sep_1 not in ["-", "/"]:

raise ValueError("Date seperator must be '-' or '/'")

# Get day

d: int = int(date_input[3] + date_input[4])

# Validate

if not 0 < d < 32:

raise ValueError("Date must be between 1 - 31")

# Get second seperator

sep_2: str = date_input[5]

# Validate

if sep_2 not in ["-", "/"]:

raise ValueError("Date seperator must be '-' or '/'")

# Get year

y: int = int(date_input[6] + date_input[7] + date_input[8] + date_input[9])

# Arbitrary year range

if not 45 < y < 8500:

raise ValueError(

"Year out of range. There has to be some sort of limit...right?"

)

# Get datetime obj for validation

dt_ck = datetime.date(int(y), int(m), int(d))

# Start math

if m <= 2:

y = y - 1

m = m + 12

# maths var

c: int = int(str(y)[:2])

k: int = int(str(y)[2:])

t: int = int(2.6 * m - 5.39)

u: int = int(c / 4)

v: int = int(k / 4)

x: int = int(d + k)

z: int = int(t + u + v + x)

w: int = int(z - (2 * c))

f: int = round(w % 7)

# End math

# Validate math

if f != convert_datetime_days[dt_ck.weekday()]:

raise AssertionError("The date was evaluated incorrectly. Contact developer.")

# Response

response: str = f"Your date {date_input}, is a {days[str(f)]}!"

return response

if __name__ == "__main__":

import doctest

doctest.testmod()

parser = argparse.ArgumentParser(

description="Find out what day of the week nearly any date is or was. Enter date as a string in the mm-dd-yyyy or mm/dd/yyyy format"

)

parser.add_argument(

"date_input", type=str, help="Date as a string (mm-dd-yyyy or mm/dd/yyyy)"

)

args = parser.parse_args()

zeller(args.date_input)