How to get which day of week is a specific date?

Question

I need to get some information about some dates and I don't know what to use. for example: I pass year, month, day (something like 1990, 5, 15) arguments to a module, and the module returns what day of week is the date we passed. I want it in Python 3.

Answer 1

If you are using a datetime.date object you can use the weekday() function. Converting to a date object inside your module should be trivial if you are passing in the day, month and year.

https://docs.python.org/3.7/library/datetime.html#datetime.date.weekday

Numeric representation

Example function:

import datetime

def weekday_from_date(day, month, year):
    return datetime.date(day=day, month=month, year=year).weekday()

Example usage:

>>> weekday_from_date(day=1, month=1, year=1995)
6

String representation

Combined with the calendar module and the day_name array you can also get it displayed as a string easily.

https://docs.python.org/3.7/library/calendar.html#calendar.day_name

Example function:

import datetime
import calendar

def weekday_from_date(day, month, year):
    return calendar.day_name[
        datetime.date(day=day, month=month, year=year).weekday()
    ]

Example usage:

>>> weekday_from_date(day=1, month=1, year=1995)
'Sunday'

Unit Tests

Using pytest writing a series of super fast unit tests should be straightforward to prove it's correctness. You can add to this suite as you please.

import pytest

@pytest.mark.parametrize(
    ['day', 'month', 'year', 'expected_weekday'],
    [
       (1, 1, 1995, 6),
       (2, 1, 1995, 0),
       (3, 1, 1995, 1),
       (6, 6, 1999, 6)
    ]
)
def test_weekday_from_date(day, month, year, expected_weekday):
    assert weekday_from_date(day, month, year) == expected_weekday

Answer 2

You can use weekday() docs. You just have to import datetime.

Answer 3

You can use weekday()

import datetime

week = ['Monday','Tuesday','Wednesday','Thursday','Friday','Saturday','Sunday']

week[datetime.datetime(1990,5,15).weekday()]

and you get:

'Tuesday'

Answer 4

You could use datetime module

from datetime import datetime

date_string = '1990, 5, 15'

date = datetime.strptime(date_string, "%Y, %m, %d")
date.weekday()

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