Yari Yari - 6 months ago 25
Python Question

Num day to Name day with Pandas

If I use this funtion

pd.DatetimeIndex(dfTrain['datetime']).weekday
I get number of the day, but I don't find any function which give the name of de day... So I need to convert 0 to Monday, 1 to Tuestday and so on.

Here is an example of my dataframe:

datetime season holiday workingday weather temp atemp humidity windspeed count
0 2011-01-01 00:00:00 1 0 0 1 9.84 14.395 81 0.0000 16
1 2011-01-01 01:00:00 1 0 0 1 9.02 13.635 80 0.0000 40
2 2011-01-01 02:00:00 1 0 0 1 9.02 13.635 80 0.0000 32
3 2011-01-01 03:00:00 1 0 0 1 9.84 14.395 75 0.0000 13
4 2011-01-01 04:00:00 1 0 0 1 9.84 14.395 75 0.0000 1
5 2011-01-01 05:00:00 1 0 0 2 9.84 12.880 75 6.0032 1
6 2011-01-01 06:00:00 1 0 0 1 9.02 13.635 80 0.0000 2
7 2011-01-01 07:00:00 1 0 0 1 8.20 12.880 86 0.0000 3
8 2011-01-01 08:00:00 1 0 0 1 9.84 14.395 75 0.0000 8
9 2011-01-01 09:00:00 1 0 0 1 13.12 17.425 76 0.0000 14


Another question more, which is the difference between
pandas.DatetimeIndex.dayofweek
and
pandas.DatetimeIndex.weekday
?

Answer

One method, so long as datetime is already a datetime column is to apply datetime.strftime to get the string for the weekday:

In [105]:

df['weekday'] = df[['datetime']].apply(lambda x: dt.datetime.strftime(x['datetime'], '%A'), axis=1)
df
Out[105]:
             datetime  season  holiday  workingday  weather   temp   atemp  \
0 2011-01-01 00:00:00       1        0           0        1   9.84  14.395   
1 2011-01-01 01:00:00       1        0           0        1   9.02  13.635   
2 2011-01-01 02:00:00       1        0           0        1   9.02  13.635   
3 2011-01-01 03:00:00       1        0           0        1   9.84  14.395   
4 2011-01-01 04:00:00       1        0           0        1   9.84  14.395   
5 2011-01-01 05:00:00       1        0           0        2   9.84  12.880   
6 2011-01-01 06:00:00       1        0           0        1   9.02  13.635   
7 2011-01-01 07:00:00       1        0           0        1   8.20  12.880   
8 2011-01-01 08:00:00       1        0           0        1   9.84  14.395   
9 2011-01-01 09:00:00       1        0           0        1  13.12  17.425   

   humidity  windspeed  count   weekday  
0        81     0.0000     16  Saturday  
1        80     0.0000     40  Saturday  
2        80     0.0000     32  Saturday  
3        75     0.0000     13  Saturday  
4        75     0.0000      1  Saturday  
5        75     6.0032      1  Saturday  
6        80     0.0000      2  Saturday  
7        86     0.0000      3  Saturday  
8        75     0.0000      8  Saturday  
9        76     0.0000     14  Saturday  

As to your other question, there is no difference between dayofweek and weekday.

It will be quicker to define a map of the weekday to String equivalent and call map on the weekday:

dayOfWeek={0:'Monday', 1:'Tuesday', 2:'Wednesday', 3:'Thursday', 4:'Friday', 5:'Saturday', 6:'Sunday'}
df['weekday'] = df['datetime'].dt.dayofweek.map(dayOfWeek)

For version prior to 0.15.0 the following should work:

import datetime as dt
df['weekday'] = df['datetime'].apply(lambda x: dt.datetime.strftime(x, '%A'))

Version 0.18.1 and newer

There is now a new convenience method dt.weekday_name to do the above

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