Iterate over every quarter of the year

Question

I am trying to iterate over every quarter of the year, this is what I have so far.

now = datetime.now()

first_day = datetime(year=now.year, month=1, day=1)
print("--",first_day)
hundredDaysLater = first_day - timedelta(days=100)

for dt in rrule.rrule(rrule.MONTHLY, dtstart=first_day, bymonthday=(31, -1), count=6, interval=3):
    print(dt.replace(day=1))
    print(dt)

output

  -- 2018-01-01 00:00:00
    2018-01-01 00:00:00
    2018-01-31 00:00:00
    2018-04-01 00:00:00
    2018-04-30 00:00:00
    2018-07-01 00:00:00
    2018-07-31 00:00:00
    2018-10-01 00:00:00
    2018-10-31 00:00:00
    2019-01-01 00:00:00
    2019-01-31 00:00:00
    2019-04-01 00:00:00

Now I basicly need to get this output

2018-01-01, 2018-03-31
2018-04-01, 2018-06-30
2018-07-01, 2018-09-30
2018-10-01, 2018-12-31

But instead of counting forwards I need to count backwards.

update your expected output due to your *"to count backwards"* — RomanPerekhrest, Dec 23 '18 at 10:51

score 2 · Accepted Answer · answered Dec 23 '18 at 10:41

Using relativedelta (from the dateutil package):

>>> from dateutil.relativedelta import relativedelta                                                                                                                  
>>> from datetime import date 
>>> d = date(2019, 1, 1)                                                                                                                                              
>>> day = relativedelta(days=1)                                                                                                                                       
>>> quarter = relativedelta(months=3)                                                                                                                                 
>>> while True: 
...     print(d - day) 
...     print(d - quarter) 
...     d -= quarter 
...                                                                                                                                                                   
2018-12-31
2018-10-01
2018-09-30
2018-07-01
2018-06-30
2018-04-01
2018-03-31
2018-01-01
2017-12-31
2017-10-01
2017-09-30
2017-07-01
2017-06-30
2017-04-01
2017-03-31
...

score 0 · Answer 2 · answered Dec 23 '18 at 13:23

Short solution with pandas.date_range function:

In [708]: start_date = datetime.datetime(2018, 1, 1)

In [709]: data = pd.date_range(start=start_date, periods=4, freq='QS-JAN').union(
                 pd.date_range(start=start_date, periods=4, freq='Q-DEC')).strftime('%Y-%m-%d')

In [710]: for i in range(0, data.size, 2):
     ...:     print(data[i], data[i+1], sep=', ')
     ...:     
2018-01-01, 2018-03-31
2018-04-01, 2018-06-30
2018-07-01, 2018-09-30
2018-10-01, 2018-12-31

Iterate over every quarter of the year

2 Answers2