Select rows between two DatetimeIndex dates

问题:

I have a CSV file of the following format:

vm,time,LoadInt1
abc-webapp-02,2017-05-31 10:00:00,3.133333
abc-webapp-02,2017-05-31 10:05:00,0.000000
abc-webapp-02,2017-05-31 10:10:00,0.000000
abc-webapp-02,2017-05-31 10:15:00,0.000000
abc-webapp-02,2017-05-31 10:20:00,0.000000
abc-webapp-02,2017-05-31 10:25:00,0.000000
abc-webapp-02,2017-05-31 10:30:00,0.000000
abc-webapp-02,2017-05-31 10:35:00,0.000000
abc-webapp-02,2017-05-31 10:40:00,0.000000

I read the CSV file into a DataFrame using the following code. The date is parsed as index (DatetimeIndex)

dateparse = lambda x: pd.datetime.strptime(x, '%Y-%m-%d %H:%M:%S')
df = pd.read_csv("my_file.csv", header=0, parse_dates=[1], index_col=1, date_parser=dateparse)

Now I am trying to get all the rows between two dates using the following code (The real CSV file has large number of rows between the dates mentioned below):

df.loc['2017-05-30' : '2017-05-31']

Please note, above approach is suggested here. But, it's not working for me. So, it may not be a duplicate question.

回答1:

Using query method:

df = pd.read_csv("my_file.csv", index_col=1, parse_dates=True)

In [121]: df.query("'2017-05-30' <= index <= '2017-06-01'")
Out[121]:
                                vm  LoadInt1
time
2017-05-31 10:00:00  abc-webapp-02  3.133333
2017-05-31 10:05:00  abc-webapp-02  0.000000
2017-05-31 10:10:00  abc-webapp-02  0.000000
2017-05-31 10:15:00  abc-webapp-02  0.000000
2017-05-31 10:20:00  abc-webapp-02  0.000000
2017-05-31 10:25:00  abc-webapp-02  0.000000
2017-05-31 10:30:00  abc-webapp-02  0.000000
2017-05-31 10:35:00  abc-webapp-02  0.000000
2017-05-31 10:40:00  abc-webapp-02  0.000000

回答2:

• This type of index slicing includes the end points and so what you have will include the entire sample set

  df.loc['2017-05-30':'2017-05-31']
  #df['2017-05-30':'2017-05-31']
  
                                  vm  LoadInt1
  time                                        
  2017-05-31 10:00:00  abc-webapp-02  3.133333
  2017-05-31 10:05:00  abc-webapp-02  0.000000
  2017-05-31 10:10:00  abc-webapp-02  0.000000
  2017-05-31 10:15:00  abc-webapp-02  0.000000
  2017-05-31 10:20:00  abc-webapp-02  0.000000
  2017-05-31 10:25:00  abc-webapp-02  0.000000
  2017-05-31 10:30:00  abc-webapp-02  0.000000
  2017-05-31 10:35:00  abc-webapp-02  0.000000
  2017-05-31 10:40:00  abc-webapp-02  0.000000
  

• This shows the same thing but actually subsets

  df.loc['2017-05-31 10:10':'2017-05-31 10:35']
  
                                  vm  LoadInt1
  time                                        
  2017-05-31 10:10:00  abc-webapp-02       0.0
  2017-05-31 10:15:00  abc-webapp-02       0.0
  2017-05-31 10:20:00  abc-webapp-02       0.0
  2017-05-31 10:25:00  abc-webapp-02       0.0
  2017-05-31 10:30:00  abc-webapp-02       0.0
  2017-05-31 10:35:00  abc-webapp-02       0.0
  

• Your import could be made smaller. You don't need the parser

  df = pd.read_csv("my_file.csv", parse_dates=[1], index_col=1)