How to convert columns into one datetime column in pandas?

In version 0.18.1 you can use to_datetime, but:

• The names of the columns have to be year, month, day, hour, minute and second:
• Minimal columns are year, month and day

Sample:

import pandas as pd

df = pd.DataFrame({'year': [2015, 2016],
                   'month': [2, 3],
                    'day': [4, 5],
                    'hour': [2, 3],
                    'minute': [10, 30],
                    'second': [21,25]})
    
print df
   day  hour  minute  month  second  year
0    4     2      10      2      21  2015
1    5     3      30      3      25  2016

print pd.to_datetime(df[['year', 'month', 'day']])
0   2015-02-04
1   2016-03-05
dtype: datetime64[ns]

print pd.to_datetime(df[['year', 'month', 'day', 'hour']])
0   2015-02-04 02:00:00
1   2016-03-05 03:00:00
dtype: datetime64[ns]

print pd.to_datetime(df[['year', 'month', 'day', 'hour', 'minute']])
0   2015-02-04 02:10:00
1   2016-03-05 03:30:00
dtype: datetime64[ns]

print pd.to_datetime(df)
0   2015-02-04 02:10:21
1   2016-03-05 03:30:25
dtype: datetime64[ns]

Another solution is convert to dictionary:

print df
   M  D     Y  Apples  Oranges
0  5  6  1990      12        3
1  5  7  1990      14        4
2  5  8  1990      15       34
3  5  9  1990      23       21

print pd.to_datetime(dict(year=df.Y, month=df.M, day=df.D))
0   1990-05-06
1   1990-05-07
2   1990-05-08
3   1990-05-09
dtype: datetime64[ns]

In 0.13 (coming very soon), this is heavily optimized and quite fast (but still pretty fast in 0.12); both orders of magnitude faster than looping

In [3]: df
Out[3]: 
   M  D     Y  Apples  Oranges
0  5  6  1990      12        3
1  5  7  1990      14        4
2  5  8  1990      15       34
3  5  9  1990      23       21

In [4]: df.dtypes
Out[4]: 
M          int64
D          int64
Y          int64
Apples     int64
Oranges    int64
dtype: object

# in 0.12, use this
In [5]: pd.to_datetime((df.Y*10000+df.M*100+df.D).apply(str),format='%Y%m%d')

# in 0.13 the above or this will work
In [5]: pd.to_datetime(df.Y*10000+df.M*100+df.D,format='%Y%m%d')
Out[5]: 
0   1990-05-06 00:00:00
1   1990-05-07 00:00:00
2   1990-05-08 00:00:00
3   1990-05-09 00:00:00
dtype: datetime64[ns]