根据日期范围中的DateTimeIndex更新列

Question

I have a Pandas dataframe with a DateTimeIndex and an empty column called HOLIDAY.

I want to set the value of that column to 'YES' if the datetime in the index is on a holiday, so that the resulting dataframe is like this:

TIME                    HOLIDAY
2019-11-25 06:00:00     NO
2019-11-26 21:00:00     NO
2019-11-27 18:00:00     NO
2019-11-28 08:00:00     YES
2019-11-29 08:00:00     NO
2019-11-30 08:00:00     NO

I have a list of dates:

holidays = ['2019-07-04', '2019-11-28','2019-12-25']
holidays = pd.to_datetime(holidays)

I tried this, but I get an error:

df.loc[df.index.date.isin(holidays), 'HOLIDAY'] = "YES"

What's the best way to achieve this?

Thank you

Answer 1

DateTimeIndex.date returns a numpy array of strings not pd.Series of pd.Timestamp dtype. So you must get the same dtype on both sides of the equality:

If TIME is not in your index this will work:

m2 = df['TIME'].dt.date.isin(holidays.date)

or

m2 = df.index.to_series().dt.date.isin(holidays.date)

df.loc[m2, 'HOLIDAY'] = "YES"

Output:

                    HOLIDAY
TIME                       
2019-11-25 06:00:00      NO
2019-11-26 21:00:00      NO
2019-11-27 18:00:00      NO
2019-11-28 08:00:00     YES
2019-11-29 08:00:00      NO
2019-11-30 08:00:00      NO

Answer 2

Note that:

• holidays contains ao 2019-11-28 at midnight ,
• your DataFrame contains ao also 2019-11-28 , but at 8:00 .

If you want to find rows with index values in holidays dates (regardless of the time part), you have to "nullify" the time part.

One of methods to get the rows in question is to use boolean indexing :

df[df.index.floor('D').isin(holidays)]

The result is:

                    HOLIDAY
TIME                       
2019-11-28 08:00:00     YES

You can also get only HOLIDAY column, running:

df[df.index.floor('D').isin(holidays)].HOLIDAY

This time the result ( Series ) is:

TIME
2019-11-28 08:00:00    YES
Name: HOLIDAY, dtype: object