为什么在比较日期后无法检索数据？

Question

无法基于日期检索数据：

df_compare = df_daily[(df_daily['INVOICE DATE'] >= From_date) & (df_daily['INVOICE DATE'] <= end_date_period1)]

From_date来自哪里

datetime_object = datetime.datetime.strptime(From_date, '%Y-%m-%d')

提供一个空的DF。

在转换为日期时间时保持低于警告状态：

Warning (from warnings module):
  File "C:\Python27\Test of Insurance_analysis_new.py", line 384
    df_daily['INVOICE DATE'] = pd.to_datetime(df_daily['INVOICE DATE'],format='%Y-%m-%d')
SettingWithCopyWarning: 
A value is trying to be set on a copy of a slice from a DataFrame.
Try using .loc[row_indexer,col_indexer] = value instead