CODEWITHSUNDEEP
python
dgel
dgel

Reputation: 16806

Calculate the end of the previous quarter

I'm looking for an elegant and pythonic way to get the date of the end of the previous quarter.

Something like this:

def previous_quarter(reference_date):
   ...


>>> previous_quarter(datetime.date(2013, 5, 31))
datetime.date(2013, 3, 31)

>>> previous_quarter(datetime.date(2013, 2, 1))
datetime.date(2012, 12, 31)

>>> previous_quarter(datetime.date(2013, 3, 31))
datetime.date(2012, 12, 31)

>>> previous_quarter(datetime.date(2013, 11, 1))
datetime.date(2013, 9, 30)

Edit: Have I tried anything?

Yes, this seems to work:

def previous_quarter(ref_date):
    current_date = ref_date - timedelta(days=1)
    while current_date.month % 3:
        current_date -= timedelta(days=1)
    return current_date

But it seems unnecessarily iterative.

Upvotes: 11

Views: 18561

Answers (9)

amine jisung
amine jisung

Reputation: 117

and if you want to retreive the last fours quarter you can do this

    if ref.month < 4:
        list1 = [datetime.date(ref.year - 1, 12, 31),
                            datetime.date(ref.year - 1, 9, 30),
                            datetime.date(ref.year - 1, 6, 30),
                            datetime.date(ref.year - 1, 3, 31)]

        list1 = [i.strftime('%Y%m%d') for i in list1]

        return list1

    elif ref.month < 7:
        return [datetime.date(ref.year, 3, 31),
                datetime.date(ref.year - 1, 12, 31),
                datetime.date(ref.year - 1, 9, 30),
                datetime.date(ref.year - 1, 6, 30)]
    elif ref.month < 10:
        return [datetime.date(ref.year, 6, 30),
                datetime.date(ref.year, 3, 31),
                datetime.date(ref.year - 1, 12, 31),
                datetime.date(ref.year - 1, 9, 30)]

    return [datetime.date(ref.year, 9, 30),
            datetime.date(ref.year, 6, 30),
            datetime.date(ref.year, 3, 30),
            datetime.date(ref.year - 1, 12, 31)]

Upvotes: 0

Smoooth Soundz
Smoooth Soundz

Reputation: 17

Reworked Justin Ethier's code for a "next quarter" version. Also added timezone via pytz and strftime formatting. @justin-ethier

import pytz
from datetime import datetime, timedelta
import datetime as dt

def nextQuarter():
    ref = datetime.now(pytz.timezone('America/New_York'))
    if ref.month < 4:
        next = dt.datetime(ref.year, 3, 31, 23, 59, 59).strftime('%m-%d-%Y %H:%M:%S')
    elif ref.month < 7:
        next = dt.datetime(ref.year, 6, 30, 23, 59, 59).strftime('%m-%d-%Y %H:%M:%S')
    elif ref.month < 10:
        next = dt.datetime(ref.year, 9, 30, 23, 59, 59).strftime('%m-%d-%Y %H:%M:%S')
    else:
        next = dt.datetime(ref.year + 1, 12, 31, 23, 59, 59).strftime('%m-%d-%Y %H:%M:%S')
    return next
next = nextQuarter()

Upvotes: 1

Sterling Paramore
Sterling Paramore

Reputation: 433

Find the first day and month of the quarter, then use relativedelta to subtract a day.

from dateutil.relativedelta import relativedelta
def previous_quarter(ref):
    first_month_of_quarter = ((ref.month - 1) // 3) * 3 + 1
    return ref.replace(month=first_month_of_quarter, day=1) - relativedelta(days=1)

Upvotes: 2

martineau
martineau

Reputation: 123491

Exploit the data pattern involved and turn the problem into a table-lookup - your classic space-time tradeff:

from datetime import date

PQTBL = (((12,31,-1),)*3 + ((3,31,0),)*3 + ((6,30,0),)*3 + ((9,30,0),)*3)

def previous_quarter(ref):
    entry = PQTBL[ref.month-1]
    return date(ref.year+entry[2], entry[0], entry[1])

Upvotes: 2

Ammar
Ammar

Reputation: 33

Solution using only python's datetime library -

import datetime

def get_quarter_end(dt):
     '''
         given a datetime object, find the end of the quarter
     '''
     quarter_of_month = int((dt.month-1)/3 + 1)
     #======================================================
     # find the first day of the next quarter
     #======================================================
     # if in last quarter then go to the next year
     year = dt.year + 1 if quarter_of_month==4 else dt.year
     # if in last quarter then month is january (or 1)
     month = 1 if quarter_of_month==4 else (quarter_of_month*3) + 1

     first_of_next_quarter = datetime.datetime(year  = year, 
                                               month = month,
                                               day   = 1
                                              )
     # last day of quarter for dt will be minus 1 day of first of next quarter
     quarter_end_dt = first_of_next_quarter - datetime.timedelta(days=1)
     return quarter_end_dt

if __name__=='__main__':
    dt = datetime.datetime.strptime('2016-07-15', '%Y-%m-%d')
    target_dt = get_quarter_end(dt)

Upvotes: 0

Tzach
Tzach

Reputation: 13396

import datetime
def previous_quarter(ref):
    quarter = (ref.month - 1) // 3
    prev_quarter = (quarter - 1) % 4
    return datetime.datetime(ref.year if quarter>0 else ref.year-1, prev_quarter*3+1, 1)

Upvotes: 0

unutbu
unutbu

Reputation: 880269

Using dateutil:

import datetime as DT
import dateutil.rrule as rrule

def previous_quarter(date):
    date = DT.datetime(date.year, date.month, date.day)
    rr = rrule.rrule(
        rrule.DAILY,
        bymonth=(3,6,9,12),    # the month must be one of these
        bymonthday=-1,         # the day has to be the last of the month
        dtstart = date-DT.timedelta(days=100))
    result = rr.before(date, inc=False)  # inc=False ensures result < date
    return result.date()

print(previous_quarter(DT.date(2013, 5, 31)))
# 2013-03-31
print(previous_quarter(DT.date(2013, 2, 1)))
# 2012-12-31
print(previous_quarter(DT.date(2013, 3, 31)))
# 2012-12-31
print(previous_quarter(DT.date(2013, 11, 1)))
# 2013-09-30

Upvotes: 5

Justin Ethier
Justin Ethier

Reputation: 134207

You can do it the "hard way" by just looking at the month you receive:

def previous_quarter(ref):
    if ref.month < 4:
        return datetime.date(ref.year - 1, 12, 31)
    elif ref.month < 7:
        return datetime.date(ref.year, 3, 31)
    elif ref.month < 10:
        return datetime.date(ref.year, 6, 30)
    return datetime.date(ref.year, 9, 30)

Upvotes: 29

U2EF1
U2EF1

Reputation: 13279

It's almost certain you would be happier using pandas (a python library), it has many functions for "business time" data.

http://pandas.pydata.org/pandas-docs/dev/timeseries.html

Upvotes: 1

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