I want to filter a pandas data frame to the last most recent 3 months.
import pandas as pd
dates = pd.DataFrame(['2016-11-01', '2016-12-01', '2017-01-01', '2017-02-01', '2017-03-01'], columns=['date'])
dates.date = pd.DatetimeIndex(dates.date)
import datetime
today = datetime.date.today()
first = today.replace(day=1)
lastMonth = first - datetime.timedelta(days=90)
print (lastMonth.strftime("%Y-%m"))
dates[dates.date >= lastMonth]
This snippet sort of already works, but has the length of a month hard coded to 30 days. How can I use a pd.Timedelta('-3 month')
(which does not seem to work like this) to achieve a more robust function?
I think you need offsets
, because Timedelta
only does not work with months:
lastMonth = first - pd.offsets.MonthBegin(3)
#lastMonth = first - pd.offsets.relativedelta(months=3)
lastMonth = first - pd.Timedelta(months=3)
ValueError: cannot construct a Timedelta from the passed arguments, allowed keywords are [weeks, days, hours, minutes, seconds, milliseconds, microseconds, nanoseconds]
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