Question

I have the following model:

Deal(models.Model):
    start_date = models.DateTimeField()
    end_date = models.DateTimeField()    

I want to iterate through a given year

year = '2010'

For each month in year I want to execute a query to see if the month is between start_date and end_date.

How can I iterate through a given year? Use the month to do a query?

SELECT * FROM deals WHERE month BETWEEN start_date AND end_date 

The outcome will tell me if I had a deal in January 2010 and/or in February 2010, etc.

Answer 1

How can I iterate through a given year?

You could use python-dateutil’s rrule. Install with command pip install python-dateutil.

Example usage:

In [1]: from datetime import datetime

In [2]: from dateutil import rrule

In [3]: list(rrule.rrule(rrule.MONTHLY, dtstart=datetime(2010,01,01,00,01), count=12))  
Out[3]: 
[datetime.datetime(2010, 1, 1, 0, 1),
 datetime.datetime(2010, 2, 1, 0, 1),
 datetime.datetime(2010, 3, 1, 0, 1),
 datetime.datetime(2010, 4, 1, 0, 1),
 datetime.datetime(2010, 5, 1, 0, 1),
 datetime.datetime(2010, 6, 1, 0, 1),
 datetime.datetime(2010, 7, 1, 0, 1),
 datetime.datetime(2010, 8, 1, 0, 1),
 datetime.datetime(2010, 9, 1, 0, 1),
 datetime.datetime(2010, 10, 1, 0, 1),
 datetime.datetime(2010, 11, 1, 0, 1),
 datetime.datetime(2010, 12, 1, 0, 1)]

Use the month to do a query?

You could iterate over months like this:

In [1]: from dateutil import rrule

In [2]: from datetime import datetime

In [3]: months = list(rrule.rrule(rrule.MONTHLY, dtstart=datetime(2010,01,01,00,01), count=13))

In [4]: i = 0

In [5]: while i < len(months) - 1:
   ...:         print "start_date", months[i], "end_date", months[i+1]
   ...:         i += 1
   ...:     
start_date 2010-01-01 00:01:00 end_date 2010-02-01 00:01:00
start_date 2010-02-01 00:01:00 end_date 2010-03-01 00:01:00
start_date 2010-03-01 00:01:00 end_date 2010-04-01 00:01:00
start_date 2010-04-01 00:01:00 end_date 2010-05-01 00:01:00
start_date 2010-05-01 00:01:00 end_date 2010-06-01 00:01:00
start_date 2010-06-01 00:01:00 end_date 2010-07-01 00:01:00
start_date 2010-07-01 00:01:00 end_date 2010-08-01 00:01:00
start_date 2010-08-01 00:01:00 end_date 2010-09-01 00:01:00
start_date 2010-09-01 00:01:00 end_date 2010-10-01 00:01:00
start_date 2010-10-01 00:01:00 end_date 2010-11-01 00:01:00
start_date 2010-11-01 00:01:00 end_date 2010-12-01 00:01:00
start_date 2010-12-01 00:01:00 end_date 2011-01-01 00:01:00

Replace the “print” statement with a query. Feel free to adapt it to your needs.

There is probably a better way but that could do the job.