Pandas QuarterBegin()：计算第一季度时可能出现错误

Question

I would like to calculate the "first of quarter" in a pandas dataframe. However I am running into some problems. My Pandas version is 0.17.1 .

import pandas as pd
import datetime as dt

test=pd.Timestamp(dt.datetime(2011,1,20))
test=test.tz_localize('Europe/Rome')

previousquarter=test-pd.tseries.offsets.QuarterBegin()
nextquarter=test+pd.tseries.offsets.QuarterBegin()

My expected results would be previousquarter = (2011,1,1) and nextquarter = (2011,4,1) . But what I get is previousquarter = (2010,12,1) and nextquarter = (2011,3,1) .

I have also tried it without tz_localize. However, it did not change the result.

Am I doing something wrong here or is this a bug somewhere?

Thanks in advance!

PS I know I could correct it by shifting one month, but this seems to be a rather crude workaround.

Answer 1

Yup, looks like a bug: https://github.com/pydata/pandas/issues/8435

There is a better workaround than shifting a month though: offsets.QuarterBegin(startingMonth=1)

Answer 2

The answer given my Marshall worked fine for me except for first days of each year where it was pointing to first date of the last quarter of the previous year. eg of 2018-01-01 I was getting 2017-10-01

I had to do the following to handle that:

(date + pd.tseries.offsets.DateOffset(days=1)) - pd.tseries.offsets.QuarterBegin(startingMonth=1) 

where date is a datetime.datetime object.

Answer 3

Reproduced @Abhi's bug in Pandas 1.1.3. In fact, couldn't get consistent results from QuarterEnd or QuarterBegin for all starting dates within the quarter. Instead resorted to going to the end of the prior quarter and adding a day, or to the beginning of the next quarter and subtracting a day. Note QuarterEnd(startingMonth= 12 )

import pandas as pd
print("     date           Quarter   Quarter begin      Quarter end   ")
for yr in range(2020, 2021):
  for mo in range(1,13):
    for dy in range(1,4):
        date = pd.Timestamp(yr, mo, dy)
        if dy == 3:
            date = date + pd.tseries.offsets.MonthEnd()
        qbegin = date + pd.offsets.QuarterEnd(-1, startingMonth=12) + pd.offsets.Day(1)
        qend = date + pd.offsets.QuarterBegin(1, startingMonth=1) - pd.offsets.Day(1)
        print("{}   {}   {}   {}".format(date, date.quarter, qbegin, qend))