Add tests for time conversions in tools package

docs/sphinx/source/whatsnew/v0.11.3.rst

@@ -12,12 +12,24 @@ Enhancements
 ~~~~~~~~~~~~
 
 
+Bug Fixes
+~~~~~~~~~
+* Ensure proper tz and pytz types in pvlib.location.Location. To ensure that
+  the time zone in pvlib.location.Location remains internally consistent
+  if/when the time zone is updated, the tz attribute is now the single source
+  of time-zone truth, is the single time-zone setter interface, and its getter 
+  returns an IANA string. (:issue:`2340`, :pull:`2341`)
+
+
 Documentation
 ~~~~~~~~~~~~~
 
 
 Testing
 ~~~~~~~
+* Add tests for timezone types in pvlib.location.Location.
+  (:issue:`2340`, :pull:`2341`)
+* Add tests for time conversions in pvlib.tools. (:issue:`2340`, :pull:`2341`)
 
 
 Requirements
@@ -31,6 +43,11 @@ Maintenance
 * asv 0.4.2 upgraded to asv 0.6.4 to fix CI failure due to pinned older conda.
   (:pull:`2352`)
 
+Breaking Changes
+~~~~~~~~~~~~~~~~
+* The pytz attribute in pvlib.location.Location is now read only. pytz time
+  zones can still be passed to tz in the object initializer and in the tz
+  setter after object creation. (:issue:`2340`, :pull:`2341`)
 
 Contributors
 ~~~~~~~~~~~~

pvlib/location.py

@@ -6,6 +6,7 @@
 
 import pathlib
 import datetime
+import zoneinfo
 
 import pandas as pd
 import pytz
@@ -18,13 +19,16 @@
 class Location:
     """
     Location objects are convenient containers for latitude, longitude,
-    timezone, and altitude data associated with a particular
-    geographic location. You can also assign a name to a location object.
+    time zone, and altitude data associated with a particular geographic
+    location. You can also assign a name to a location object.
 
-    Location objects have two timezone attributes:
+    Location objects have two time-zone attributes:
 
-        * ``tz`` is a IANA timezone string.
-        * ``pytz`` is a pytz timezone object.
+        * ``tz`` is an IANA time-zone string.
+        * ``pytz`` is a pytz-based time-zone object (read only).
+
+    The read-only ``pytz`` attribute will stay in sync with any changes made
+    using ``tz``.
 
     Location objects support the print method.
 
@@ -38,12 +42,15 @@ class Location:
         Positive is east of the prime meridian.
         Use decimal degrees notation.
 
-    tz : str, int, float, or pytz.timezone, default 'UTC'.
-        See
-        http://en.wikipedia.org/wiki/List_of_tz_database_time_zones
-        for a list of valid time zones.
-        pytz.timezone objects will be converted to strings.
-        ints and floats must be in hours from UTC.
+    tz : time zone as str, int, float, or datetime.tzinfo, default 'UTC'.
+        This value represents as a valid IANA time zone name string. See
+        http://en.wikipedia.org/wiki/List_of_tz_database_time_zones for a
+        list of valid name strings, any of which may be passed directly here.
+        ints and floats must be whole-number hour offsets from UTC, which
+        are converted to the IANA-suppored 'Etc/GMT-N' format. (Note the
+        limited range of the offset N and its sign-change convention.)
+        Time zones from the pytz and zoneinfo packages may also be passed
+        directly here, as they are subclasses of datetime.tzinfo.
 
     altitude : float, optional
         Altitude from sea level in meters.
@@ -54,43 +61,75 @@ class Location:
     name : string, optional
         Sets the name attribute of the Location object.
 
+    Raises
+    ------
+    ValueError
+        when the time-zone ``tz`` input cannot be converted.
+
+    zoneinfo.ZoneInfoNotFoundError
+        when the time zone ``tz`` is not recognizable as an IANA time zone by
+        the ``zoneinfo.ZoneInfo`` initializer used for internal time-zone
+        representation.
+
     See also
     --------
     pvlib.pvsystem.PVSystem
     """
 
-    def __init__(self, latitude, longitude, tz='UTC', altitude=None,
-                 name=None):
-
+    def __init__(
+        self, latitude, longitude, tz='UTC', altitude=None, name=None
+    ):
         self.latitude = latitude
         self.longitude = longitude
-
-        if isinstance(tz, str):
-            self.tz = tz
-            self.pytz = pytz.timezone(tz)
-        elif isinstance(tz, datetime.timezone):
-            self.tz = 'UTC'
-            self.pytz = pytz.UTC
-        elif isinstance(tz, datetime.tzinfo):
-            self.tz = tz.zone
-            self.pytz = tz
-        elif isinstance(tz, (int, float)):
-            self.tz = tz
-            self.pytz = pytz.FixedOffset(tz*60)
-        else:
-            raise TypeError('Invalid tz specification')
+        self.tz = tz
 
         if altitude is None:
             altitude = lookup_altitude(latitude, longitude)
 
         self.altitude = altitude
-
         self.name = name
 
     def __repr__(self):
         attrs = ['name', 'latitude', 'longitude', 'altitude', 'tz']
+        # Use None as getattr default in case __repr__ is called during
+        # initialization before all attributes have been assigned.
         return ('Location: \n  ' + '\n  '.join(
-            f'{attr}: {getattr(self, attr)}' for attr in attrs))
+            f'{attr}: {getattr(self, attr, None)}' for attr in attrs))
+
+    @property
+    def tz(self):
+        """The location's IANA time-zone string."""
+        return str(self._zoneinfo)
+
+    @tz.setter
+    def tz(self, tz_):
+        # self._zoneinfo holds single source of time-zone truth as IANA name.
+        if isinstance(tz_, str):
+            self._zoneinfo = zoneinfo.ZoneInfo(tz_)
+        elif isinstance(tz_, int):
+            self._zoneinfo = zoneinfo.ZoneInfo(f"Etc/GMT{-tz_:+d}")
+        elif isinstance(tz_, float):
+            if tz_ % 1 != 0:
+                raise TypeError(
+                    "Floating-point tz has non-zero fractional part: "
+                    f"{tz_}. Only whole-number offsets are supported."
+                )
+
+            self._zoneinfo = zoneinfo.ZoneInfo(f"Etc/GMT{-int(tz_):+d}")
+        elif isinstance(tz_, datetime.tzinfo):
+            # Includes time zones generated by pytz and zoneinfo packages.
+            self._zoneinfo = zoneinfo.ZoneInfo(str(tz_))
+        else:
+            raise TypeError(
+                f"invalid tz specification: {tz_}, must be an IANA time zone "
+                "string, a whole-number int/float UTC offset, or a "
+                "datetime.tzinfo object (including subclasses)"
+            )
+
+    @property
+    def pytz(self):
+        """The location's pytz time zone (read only)."""
+        return pytz.timezone(str(self._zoneinfo))
 
     @classmethod
     def from_tmy(cls, tmy_metadata, tmy_data=None, **kwargs):

pvlib/tests/test_location.py

@@ -1,5 +1,6 @@
 import datetime
 from unittest.mock import ANY
+import zoneinfo
 
 import numpy as np
 from numpy import nan
@@ -9,7 +10,6 @@
 import pytest
 
 import pytz
-from pytz.exceptions import UnknownTimeZoneError
 
 import pvlib
 from pvlib import location
@@ -27,22 +27,63 @@ def test_location_all():
     Location(32.2, -111, 'US/Arizona', 700, 'Tucson')
 
 
-@pytest.mark.parametrize('tz', [
-    pytz.timezone('US/Arizona'), 'America/Phoenix',  -7, -7.0,
-    datetime.timezone.utc
-])
-def test_location_tz(tz):
-    Location(32.2, -111, tz)
-
-
-def test_location_invalid_tz():
-    with pytest.raises(UnknownTimeZoneError):
-        Location(32.2, -111, 'invalid')
-
-
-def test_location_invalid_tz_type():
+@pytest.mark.parametrize(
+    'tz,tz_expected', [
+        pytest.param('UTC', 'UTC'),
+        pytest.param('Etc/GMT+5', 'Etc/GMT+5'),
+        pytest.param('US/Mountain', 'US/Mountain'),
+        pytest.param('America/Phoenix', 'America/Phoenix'),
+        pytest.param('Asia/Kathmandu', 'Asia/Kathmandu'),
+        pytest.param('Asia/Yangon', 'Asia/Yangon'),
+        pytest.param(datetime.timezone.utc, 'UTC'),
+        pytest.param(zoneinfo.ZoneInfo('Etc/GMT-7'), 'Etc/GMT-7'),
+        pytest.param(pytz.timezone('US/Arizona'), 'US/Arizona'),
+        pytest.param(-6, 'Etc/GMT+6'),
+        pytest.param(-11.0, 'Etc/GMT+11'),
+        pytest.param(12, 'Etc/GMT-12'),
+    ],
+)
+def test_location_tz(tz, tz_expected):
+    loc = Location(32.2, -111, tz)
+    assert isinstance(loc.pytz, datetime.tzinfo)  # Abstract base class.
+    assert isinstance(loc.pytz, pytz.tzinfo.BaseTzInfo)
+    assert type(loc.tz) is str
+    assert loc.tz == tz_expected
+
+
+def test_location_tz_update():
+    loc = Location(32.2, -111, -11)
+    assert loc.tz == 'Etc/GMT+11'
+    assert loc.pytz == pytz.timezone('Etc/GMT+11')  # Deprecated attribute.
+
+    # Updating Location's tz updates read-only time-zone attributes.
+    loc.tz = 7
+    assert loc.tz == 'Etc/GMT-7'
+    assert loc.pytz == pytz.timezone('Etc/GMT-7')  # Deprecated attribute.
+
+
+@pytest.mark.parametrize(
+    'tz', [
+        'invalid',
+        'Etc/GMT+20',  # offset too large.
+        20,  # offset too large.
+    ]
+)
+def test_location_invalid_tz(tz):
+    with pytest.raises(zoneinfo.ZoneInfoNotFoundError):
+        Location(32.2, -111, tz)
+
+
+@pytest.mark.parametrize(
+    'tz', [
+        -9.5,  # float with non-zero fractional part.
+        b"bytes not str",
+        [5],
+    ]
+)
+def test_location_invalid_tz_type(tz):
     with pytest.raises(TypeError):
-        Location(32.2, -111, [5])
+        Location(32.2, -111, tz)
 
 
 def test_location_print_all():