subtract dates with time module

[John Machin]

barronmo wrote:
> I'm trying to get the difference in dates using the time module rather
> than datetime because I need to use strptime() to convert a date and
> then find out how many weeks and days until that date. 

datetime.datetime.strptime was introduced in Python 2.5; what version 
are you using?

If you really want to get to datetime, here's a quick bridge:
 >>> import time, datetime
 >>> def mystrptime(astr, format):
...     return datetime.datetime(*time.strptime(astr, format)[:6])
...
 >>> mystrptime('2008-03-31', '%Y-%m-%d')
datetime.datetime(2008, 3, 31, 0, 0)


> I'm a beginner
> so any help would be appreciated.  Here is the code:
> 
> def OBweeks(ptID):
>      qry = 'SELECT short_des FROM problems WHERE patient_ID = %s;'  %
> (ptID)
>      results = EMR_utilities.getAllData(qry)
>      for items in results:
>           r = re.search('\d\d\d\d-\d\d-\d\d', items)
>           if r:
>                d = time.strptime(r.group(), "%Y-%m-%d')  -

You have " at the start and ' at the end of what's supposed to be a 
string constant. That's a syntax error; it won't run. Please don't serve 
up what you thought you might have run -- use copy/paste.

In this particular case, you can just use time.mktime to convert a time 
tuple into days since the epoch.

# untested
days = time.mktime(time.strptime(r.group(), "%Y-%m-%d")) - 
int(time.mktime(time.localtime()))
weeks, days = divmod(days, 7)

> time.localtime()
>                weeks, days  = divmod(d.days, 7)
>                return '%s %s/7 weeks'  % (weeks, days)
> 
> This isn't working.  I'm getting "unsupported operand type for -:
> 'time.struct_time' and 'time.struct_time" error.

It *is* working. That is the correct result of the code that you 
executed. There is is nothing in the time docs to suggest that 
attempting to subtract time tuples produces anything useful.

HTH,
John