Johan Nilssons Lifestream

pandas filter dates to last most recent 3 months

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']) = pd.DatetimeIndex(
import datetime
today =
first = today.replace(day=1)
lastMonth = first - datetime.timedelta(days=90)
print (lastMonth.strftime("%Y-%m"))
dates[ >= 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?

via Stack Overflow

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