Get yesterday's date in Python, DST-safe

Question

I have a python script that uses this call to get yesterday's date in YYYY-MM-DD format:

str(date.today() - timedelta(days=1))) 

It works most of the time, but when the script ran this morning at 2013-03-11 0:35 CDT it returned "2013-03-09" instead of "2013-03-10".

Presumably daylight saving time (which started yesterday) is to blame. I guess the way timedelta(days=1) is implemented it subtracted 24 hours, and 24 hours before 2013-03-11 0:35 CDT was 2013-03-09 23:35 CST, which led to the result of "2013-03-09".

So what's a good DST-safe way to get yesterday's date in python?

UPDATE: After bukzor pointed out that my code should have worked properly, I went back to the script and determined it wasn't being used. It sets the default value, but a wrapper shell script was setting the date explicitly. So the bug is in the shell script, not the python script.

Answer 1

datetime.date.fromordinal(datetime.date.today().toordinal()-1) 

Answer 2

I'm not able to reproduce your issue in python2.7 or python3.2:

>>> import datetime >>> today = datetime.date(2013, 3, 11) >>> print today 2013-03-11 >>> day = datetime.timedelta(days=1) >>> print today - day 2013-03-10 

It seems to me that this is already the simplest implementation of a "daylight-savings safe" yesterday() function.