Python elegant way of finding the last weekday

Question

I need to find the last weekday (without considering holidays). Is there any more elegant/robust way of implementing this than the one I'm currently using?

from datetime import date
b = date.today() - timedelta(days=1)
while b.weekday()>=5:
    b = b - timedelta(days=1)

Sorry probably it is me but I don't get it :D last of what? of the month, of the year? — Giovanni Frison, Apr 01 '21 at 07:49
Given a date, I need to find the last weekday. I.e. if Sunday, then Friday, if Wednesday, then Tuesday, if Monday, then Friday. — Javi Torre, Apr 01 '21 at 07:50
You mean "find the last *business day* before today", right? Your examples indicate you are searching for Mo-Fr days only, right? — ojdo, Apr 01 '21 at 07:58
I think the solution you have is pretty elegant as it is quite readable. the same question has been asked before and the accepted answer offers the solution you already have: [previous-weekday-in-python](https://stackoverflow.com/questions/12053633/previous-weekday-in-python). — Krishna Chaurasia, Apr 01 '21 at 07:59
@JaviTorre, do you need to perform this calculation at least 20 times? — Michael Ruth, Apr 01 '21 at 08:29
@JaviTorre, then efficiency doesn't matter so you can sacrifice it for readability and clear intent. I think your solution is clear. Bas Swinckels's answer is a bit more elegant. The lookup table method in the [duplicate](https://stackoverflow.com/questions/12053633/previous-weekday-in-python) is the most efficient but is slightly magical, not much, it's fairly obvious what's going on but it does sacrifice a little clarity for efficiency. — Michael Ruth, Apr 01 '21 at 17:15

Bas Swinckels · Accepted Answer · 2021-04-01T08:03:15.437

1

Something like this might work (untested):

from datetime import date, timedelta
b = date.today() - timedelta(days=1)

current_day = b.weekday()  # 0 for Monday, 6 for Sunday

# go back 1 day for Sat, 2 days for Sun, 0 for other days
days_to_go_back = max(current_day - 4, 0)  

b -= timedelta(days=days_to_go_back)

edited Apr 01 '21 at 08:03

answered Apr 01 '21 at 07:58

Bas Swinckels

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Python elegant way of finding the last weekday

1 Answers1