ENH: Use datetutil.tz.gettz() instead of dateutil.zoneinfo.gettz()

python-dateutil provides two implementations for gettz(), tz.gettz() and
zoneinfo.gettz(). The former tries first to use system provided timezone data,
where as the later always uses a bundled tarball. Upstreams recommandation
for library consumers is only using tz.gettz() (1 & 2). Further more, on
system which do not install the zoninfo tarball (e.g. Debian, Gentoo and
Fedora) but rely on the system zoneinfo files the direct usage of
zoneinfo.gettz() creates problems which result in test failures (3 - 6).

For compatibility in pandas code

    pandas.tslib._dateutil_gettz()

should be used.

1 dateutil/dateutil#8
2 dateutil/dateutil#11
3 pandas-dev#9059
4 pandas-dev#8639
5 pandas-dev#10121
6 pandas-dev#9663

Signed-off-by: Justin Lecher <jlec@gentoo.org>

doc/source/whatsnew/v0.17.0.txt

@@ -26,6 +26,26 @@ New features
 Other enhancements
 ^^^^^^^^^^^^^^^^^^
 
+- Add helper functions to check for OS running on
+
+  from pandas.compat import is_platform_windows
+  if is_platform_window():
+      pass
+
+- Use dateutil.tz.gettz() after upstream recommandations
+
+  python-dateutil provides two implementations of gettz().
+  "dateutil.tz.gettz()" tries to load zone information from system provided data and fals back to 
+  an included tarball, where as "dateutil.zoneinfo.gettz() loads directly from the tarball. Using the later on systems
+  which aren't providing included zone informations (e.g. Fedora or Gentoo) breaks (#9059, #8639, #9663 and #10121)
+  As stated by upstream in https://github.com/dateutil/dateutil/issues/11#issuecomment-70769019 only the former should be
+  used by library consumers.
+
+  For compatibility in pandas following code should be used
+
+  from pandas.tslib import _dateutil_gettz as gettz
+  tz = gettz('Europe/Brussels')
+
 .. _whatsnew_0170.api:
 
 Backwards incompatible API changes
@@ -66,5 +86,4 @@ Bug Fixes
 - Bug in ``Timestamp``'s' ``microsecond``, ``quarter``, ``dayofyear``, ``week`` and ``daysinmonth`` properties return ``np.int`` type, not built-in ``int``. (:issue:`10050`)
 - Bug in ``NaT`` raises ``AttributeError`` when accessing to ``daysinmonth``, ``dayofweek`` properties. (:issue:`10096`)
 
-
-
+- Bug in dateutil.tz.gettz() vs. dateutil.zoneinfo.gettz() usage which creates problems on systems solely rely on systems timezone data (:issue:`9123`, :issue:`9059`, :issue:`8639`, :issue:`9663`, :issue:`10121`)

pandas/compat/__init__.py

@@ -26,6 +26,7 @@
 
 Other items:
 * OrderedDefaultDict
+* platform checker
 """
 # pylint disable=W0611
 import functools
@@ -754,3 +755,16 @@ def __missing__(self, key):
     def __reduce__(self):  # optional, for pickle support
         args = self.default_factory if self.default_factory else tuple()
         return type(self), args, None, None, list(self.items())
+
+
+# https://github.com/pydata/pandas/pull/9123
+def is_platform_windows():
+    return sys.platform == 'win32' or sys.platform == 'cygwin'
+
+
+def is_platform_linux():
+    return sys.platform == 'linux2'
+
+
+def is_platform_mac():
+    return sys.platform == 'darwin'

pandas/tests/test_series.py

@@ -5398,7 +5398,8 @@ def test_getitem_setitem_datetime_tz_pytz(self):
     def test_getitem_setitem_datetime_tz_dateutil(self):
         tm._skip_if_no_dateutil();
         from dateutil.tz import tzutc
-        from dateutil.tz import gettz
+        from pandas.tslib import _dateutil_gettz as gettz
+
         tz = lambda x: tzutc() if x == 'UTC' else gettz(x)  # handle special case for utc in dateutil
 
         from pandas import date_range

pandas/tseries/tests/test_daterange.py

@@ -441,7 +441,7 @@ def test_month_range_union_tz_pytz(self):
     def test_month_range_union_tz_dateutil(self):
         _skip_if_windows_python_3()
         tm._skip_if_no_dateutil()
-        from dateutil.tz import gettz as timezone
+        from pandas.tslib import _dateutil_gettz as timezone
         tz = timezone('US/Eastern')
 
         early_start = datetime(2011, 1, 1)

pandas/tseries/tests/test_period.py

@@ -101,15 +101,15 @@ def test_timestamp_tz_arg(self):
                          pytz.timezone('Europe/Brussels').normalize(p).tzinfo)
 
     def test_timestamp_tz_arg_dateutil(self):
-        import dateutil
+        from pandas.tslib import _dateutil_gettz as gettz
         from pandas.tslib import maybe_get_tz
         p = Period('1/1/2005', freq='M').to_timestamp(tz=maybe_get_tz('dateutil/Europe/Brussels'))
-        self.assertEqual(p.tz, dateutil.tz.gettz('Europe/Brussels'))
+        self.assertEqual(p.tz, gettz('Europe/Brussels'))
 
     def test_timestamp_tz_arg_dateutil_from_string(self):
-        import dateutil
+        from pandas.tslib import _dateutil_gettz as gettz
         p = Period('1/1/2005', freq='M').to_timestamp(tz='dateutil/Europe/Brussels')
-        self.assertEqual(p.tz, dateutil.tz.gettz('Europe/Brussels'))
+        self.assertEqual(p.tz, gettz('Europe/Brussels'))
 
     def test_timestamp_nat_tz(self):
         t = Period('NaT', freq='M').to_timestamp()

pandas/tseries/tests/test_timeseries.py

@@ -417,9 +417,9 @@ def test_timestamp_to_datetime_explicit_pytz(self):
     def test_timestamp_to_datetime_explicit_dateutil(self):
         _skip_if_windows_python_3()
         tm._skip_if_no_dateutil()
-        import dateutil
+        from pandas.tslib import _dateutil_gettz as gettz
         rng = date_range('20090415', '20090519',
-                         tz=dateutil.tz.gettz('US/Eastern'))
+                         tz=gettz('US/Eastern'))
 
         stamp = rng[0]
         dtval = stamp.to_pydatetime()
@@ -1807,7 +1807,7 @@ def test_append_concat_tz_explicit_pytz(self):
     def test_append_concat_tz_dateutil(self):
         # GH 2938
         tm._skip_if_no_dateutil()
-        from dateutil.tz import gettz as timezone
+        from pandas.tslib import _dateutil_gettz as timezone
 
         rng = date_range('5/8/2012 1:45', periods=10, freq='5T',
                          tz='dateutil/US/Eastern')

pandas/tslib.pyx

@@ -41,7 +41,11 @@ from datetime import time as datetime_time
 # dateutil compat
 from dateutil.tz import (tzoffset, tzlocal as _dateutil_tzlocal, tzfile as _dateutil_tzfile,
                          tzutc as _dateutil_tzutc)
-from dateutil.tz import gettz as _dateutil_gettz
+from pandas.compat import is_platform_windows
+if is_platform_windows():
+    from dateutil.zoneinfo import gettz as _dateutil_gettz
+else:
+    from dateutil.tz import gettz as _dateutil_gettz
 
 from pytz.tzinfo import BaseTzInfo as _pytz_BaseTzInfo
 from pandas.compat import parse_date, string_types, PY3, iteritems