python - 创建每月的 pandas DatetimeIndex

Question

我有一个包含 12 个值的数据框，我想将其转换为 DatetimeIndex 类型

months = df['date'] #e.g. '2016-04-01'
idx = pd.date_range(months[0], months[11], freq='M')

但是，生成的DatetimeIndex长度只有11，应该是12不确定是否是因为频率的原因，将日期移至月末？

Answer 1

对我来说，工作是用句点生成的:

print df
         date
0  2016-01-01
1  2016-02-01
2  2016-03-01
3  2016-04-02

print pd.date_range(df['date'].iloc[0], periods=12, freq='M')
DatetimeIndex(['2016-01-31', '2016-02-29', '2016-03-31', '2016-04-30',
               '2016-05-31', '2016-06-30', '2016-07-31', '2016-08-31',
               '2016-09-30', '2016-10-31', '2016-11-30', '2016-12-31'],
              dtype='datetime64[ns]', freq='M')

为什么最后一个值缺失 - check in the end :

months = df['date'] 
print pd.date_range(months.iloc[0], months.iloc[3], freq='M')
DatetimeIndex(['2016-01-31', '2016-02-29', '2016-03-31'], dtype='datetime64[ns]', freq='M')

The start and end dates are strictly inclusive. So it will not generate any dates outside of those dates if specified.