Find Monday's date with Python
ChristopheD's post is close to what you want. I don't have enough rep to make a comment :(
Instead of (which actually gives you the next upcoming monday):

>>> today + datetime.timedelta(days=-today.weekday(), weeks=1)
datetime.date(2009, 10, 26)

I would say:

>>> last_monday = today - datetime.timedelta(days=today.weekday())

If you want the previous week, add the 'weeks=1' parameter.
This makes the code more readable since you are subtracting a timedelta. This clears up any confusion caused by adding a timedelta that has negative and positive offsets.
How do I find the previous Monday's date, based off of the current date using Python? I thought maybe I could use: datetime.weekday() to do it, but I am getting stuck.
I basically want to find today's date and Mondays date to construct a date range query in django using: created__range=(start_date, end_date).