Pandas dataframe with column of timestamps and timezones

Question

I have a pandas dataframe with a column of timestamps and a column of timezones the timestamps are in. What's the best way to convert all these timestamps to UTC time?

Sample data in csv:

0,2000-01-28 16:47:00,America/Chicago
1,2000-01-29 16:48:00,America/Chicago
2,2000-01-30 16:49:00,America/Los_Angeles
3,2000-01-31 16:50:00,America/Chicago
4,2000-01-01 16:50:00,America/New_York

Answer 1

This can be efficiently done by converting a single tz at a time (but since we have many, groupby already separates these out). These are local times (IOW in the given timezone), so tz_localize makes these tz-aware. Then when we combine them these are auto-magically converted to UTC.

Note this is on master/0.17.0, releasing soon. Soln for < 0.17.0 is below

In [19]: df = read_csv(StringIO(data),header=None, names=['value','date','tz'])

In [20]: df.dtypes
Out[20]: 
value     int64
date     object
tz       object
dtype: object

In [21]: df
Out[21]: 
   value                 date                   tz
0      0  2000-01-28 16:47:00      America/Chicago
1      1  2000-01-29 16:48:00      America/Chicago
2      2  2000-01-30 16:49:00  America/Los_Angeles
3      3  2000-01-31 16:50:00      America/Chicago
4      4  2000-01-01 16:50:00     America/New_York

In [22]: df['utc'] = df.groupby('tz').date.apply(
                lambda x: pd.to_datetime(x).dt.tz_localize(x.name))

In [23]: df
Out[23]: 
   value                 date                   tz                 utc
0      0  2000-01-28 16:47:00      America/Chicago 2000-01-28 22:47:00
1      1  2000-01-29 16:48:00      America/Chicago 2000-01-29 22:48:00
2      2  2000-01-30 16:49:00  America/Los_Angeles 2000-01-31 00:49:00
3      3  2000-01-31 16:50:00      America/Chicago 2000-01-31 22:50:00
4      4  2000-01-01 16:50:00     America/New_York 2000-01-01 21:50:00

In [24]: df.dtypes
Out[24]: 
value             int64
date             object
tz               object
utc      datetime64[ns]
dtype: object

In < 0.17.0, need to:

df['utc'] = df['utc'].dt.tz_localize(None)

to convert to UTC

Answer 2

In general: combine the 2 csv time columns during the import (or before). This can be done with a small lambda-function.

To convert (parse) that combined info, several options exist. Most are described here or in the pandas-docs. Personally I like the utils.parse one.