DataFrame groupby partially drops timezone info (to_csv, in notebook)

[Poquaruse]

Hi all,

I've encountered a problem with DataFrames, groupby and timezones.

import pandas as pd
import numpy as np

dt_rng = pd.date_range(start='2014-01-01 00:00', periods = 1000, freq='1s', tz='Europe/Berlin')
df = pd.DataFrame({'a':np.random.randn(1000), 'b': np.random.randn(1000)},index = dt_rng)
df['b'] = df['b'].round()
df.to_csv()

--> Timezones are shown in the csv output, for example 2014-01-01 00:00:00+01:00

Now with resampling:

dt_rng = pd.date_range(start='2014-01-01 00:00', periods = 1000, freq='1s', tz='Europe/Berlin')
df = pd.DataFrame({'a':np.random.randn(1000), 'b': np.random.randn(1000)},index = dt_rng)
df['b'] = df['b'].round()
df.groupby(df['b']).resample('1min').to_csv()

--> 2013-12-31 23:01:00 no timezone info, not even UTC.

However:

dt_rng = pd.date_range(start='2014-01-01 00:00', periods = 1000, freq='1s', tz='Europe/Berlin')
df = pd.DataFrame({'a':np.random.randn(1000), 'b': np.random.randn(1000)},index = dt_rng)
df['b'] = df['b'].round()
df.groupby(df['b']).resample('1min').index.levels[1]

shows: Timezone: Europe/Berlin

So the info seems to be there, but is not exported - even if it was exported before without resampling...

Any ideas?

Thanks and best regards

[jreback]

pls post pd.show_versions()

[Poquaruse]

Sorry, I forgot. Here it is:

INSTALLED VERSIONS

commit: None
python: 3.4.1.final.0
python-bits: 64
OS: Windows
OS-release: 8
machine: AMD64
processor: Intel64 Family 6 Model 58 Stepping 9, GenuineIntel
byteorder: little
LC_ALL: None
LANG: None

pandas: 0.14.0
nose: 1.3.3
Cython: 0.20.1
numpy: 1.8.1
scipy: 0.14.0
statsmodels: None
IPython: 2.1.0
sphinx: 1.2.2
patsy: 0.2.1
scikits.timeseries: None
dateutil: 2.1
pytz: 2014.3
bottleneck: None
tables: 3.1.1
numexpr: 2.3.1
matplotlib: 1.3.1
openpyxl: 1.8.5
xlrd: 0.9.3
xlwt: None
xlsxwriter: 0.5.5
lxml: 3.3.5
bs4: 4.3.1
html5lib: None
bq: None
apiclient: None
rpy2: None
sqlalchemy: 0.9.4
pymysql: None
psycopg2: None

[jreback]

this works in master, lots of bugs related to tz preservation are fixed for 0.14.1 (releasing soon)

[Poquaruse]

Thanks for the heads up! :-)