(Python) Find next weekday or last weekday

last_or_next_weekday.py

from datetime import timedelta


def next_weekday(date, weekday):
    day_gap = weekday - date.weekday()
    if day_gap <= 0:
        day_gap += 7
    return date + timedelta(days=day_gap)


def last_weekday(date, weekday):
    day_gap = weekday - date.weekday()
    if day_gap >= 0:
        day_gap -= 7
    return date + timedelta(days=day_gap)

test_weekday.py

import unittest
from datetime import datetime
from weekday import next_weekday, last_weekday

fmt = '%Y-%m-%d'
date = datetime(2015, 5, 1)


class WeekdayTestCase(unittest.TestCase):
    def test_last_week_day(self):
        self.assertEqual(last_weekday(date, 0).strftime(fmt), '2015-04-27')
        self.assertEqual(last_weekday(date, 1).strftime(fmt), '2015-04-28')
        self.assertEqual(last_weekday(date, 2).strftime(fmt), '2015-04-29')
        self.assertEqual(last_weekday(date, 3).strftime(fmt), '2015-04-30')
        self.assertEqual(last_weekday(date, 4).strftime(fmt), '2015-04-24')
        self.assertEqual(last_weekday(date, 5).strftime(fmt), '2015-04-25')
        self.assertEqual(last_weekday(date, 6).strftime(fmt), '2015-04-26')

    def test_next_week_day(self):
        self.assertEqual(next_weekday(date, 0).strftime(fmt), '2015-05-04')
        self.assertEqual(next_weekday(date, 1).strftime(fmt), '2015-05-05')
        self.assertEqual(next_weekday(date, 2).strftime(fmt), '2015-05-06')
        self.assertEqual(next_weekday(date, 3).strftime(fmt), '2015-05-07')
        self.assertEqual(next_weekday(date, 4).strftime(fmt), '2015-05-08')
        self.assertEqual(next_weekday(date, 5).strftime(fmt), '2015-05-02')
        self.assertEqual(next_weekday(date, 6).strftime(fmt), '2015-05-03')

if __name__ == '__main__':
    unittest.main()

last_weekday 这个函数不对,
当我使用weekday形参为0时,用2019年8月20号(星期二)的带入进去,算出上个星期是2019年8月19号(昨天),而正确答案是2019年8月12号(星期一),
而当我把weekday形参设为1时,计算出时间是2019年8月13号,所以当weekday为0时应该要算出2019年8月12号的

因此,last_weekday函数应该是:

def last_weekday(date, weekday):
    day_gap = weekday - date.weekday()
    day_gap -= 7
    return date + timedelta(days=day_gap)