Pandas过滤日期为最近3个月

Question

我想过滤最近3个月的熊猫数据框。在

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]

这段代码已经可以使用了，但是一个月的长度被硬编码为30天。如何使用pd.Timedelta('-3 month')（它似乎不是这样工作的）来实现一个更健壮的函数？在

Answer 1

我认为您需要^{}，因为Timedelta仅适用于月份：

lastMonth = first - pd.offsets.MonthBegin(3)
#lastMonth = first - pd.offsets.relativedelta(months=3)

---

^{pr2}$

ValueError: cannot construct a Timedelta from the passed arguments, allowed keywords are [weeks, days, hours, minutes, seconds, milliseconds, microseconds, nanoseconds]