ENH: support pendulum objects

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

[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.

[philsheard]

I see that the Pendulum issue has been closed without a fix, so if anyone wants a workaround to this:

I did a roundtrip from Pendulum > ISO format > Pandas to avoid the internal lookup that causes the warning.

converted_date = pandas.to_datetime(pendulum.today().isoformat())

Not pretty but it will clean your error logs without hurting comprehension.