ENH: support pendulum objects

[ericgazoni]

import pendulum
import pandas
pandas.date_range(start=pendulum.now(), end=pendulum.tomorrow())

[1]    56829 segmentation fault  ipython

Problem description

As pendulum claims to inherit from datetime.datetime, I wouldn't expect a segfaut to happen, as date_range always worked find with datetime objects

From the documentation:

The Pendulum class is a drop-in replacement for the native datetime class (it is inherited from it).

I could file an issue on the pendulum bug tracker as well, but that's pandas who's segfaulting, so I think you guys would have better tools to understand what's going on.

Expected Output

DatetimeIndex(['2017-04-12 20:54:52.305104', '2017-04-13 20:54:52.305104'], dtype='datetime64[ns]', freq='D')

Output of pd.show_versions()

INSTALLED VERSIONS

commit: None
python: 3.5.2.final.0
python-bits: 64
OS: Darwin
OS-release: 15.6.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: None
LANG: fr_BE.UTF-8
LOCALE: fr_BE.UTF-8

pandas: 0.19.2
nose: None
pip: 9.0.1
setuptools: 34.4.1
Cython: None
numpy: 1.12.1
scipy: None
statsmodels: None
xarray: None
IPython: 5.3.0
sphinx: None
patsy: None
dateutil: 2.6.0
pytz: 2017.2
blosc: None
bottleneck: None
tables: None
numexpr: None
matplotlib: None
openpyxl: None
xlrd: 1.0.0
xlwt: None
xlsxwriter: None
lxml: None
bs4: None
html5lib: None
httplib2: None
apiclient: None
sqlalchemy: 1.1.9
pymysql: None
psycopg2: 2.6.2 (dt dec pq3 ext lo64)
jinja2: 2.9.6
boto: None
pandas_datareader: None

[jreback]

this is a pendulum issue. They don't use standard timezones.

In [4]: type(pendulum.now().tz)
Out[4]: pendulum.tz.timezone.Timezone

we accept dateutil and pytz timezones. I suppose we could add (optional) support for this. but all we would do would be to convert to Timestamp anyhow, but it would likely be a major effort for not much gain.

closing this as won't fix / out-of-scope.

[sdispater]

@jreback Author of pendulum here :-) What do you mean by it does not use standard timezone?

>>> isinstance(pendulum.now().tzinfo, datetime.tzinfo)
True

So, as you can see, pendulum uses a subclass of the standard tzinfo.

The underlying problem comes from pandas since it calls:

int(total_seconds(_get_utcoffset(tz, None)))

in the _get_dst_info() function.

However total_seconds() assumes a timedelta while the utcoffset() method of a tzinfo can also return None.

Here is what the offical Python documentation says (https://docs.python.org/3.6/library/datetime.html#datetime.tzinfo.utcoffset):

If the UTC offset isn’t known, return None.

And in this case None is being passed to utcoffset() so there is no way to determine the offset that's why pendulum returns None.

So None is a valid return value, however pandas will segfault when it occurs.

[TomAugspurger]

Thanks for the explanation @sdispater.