Change get_pvgis_tmy coerce_year default to 1990 (#2474)

* Change get_pvgis_tmy coerce_year default to 1990

* Update tests

* Add whatsnew

* Specific testing of default coerce_year value

* Apply suggestions from code review

Co-authored-by: Kevin Anderson <kevin.anderso@gmail.com>

* Update pvlib/iotools/pvgis.py

Co-authored-by: Kevin Anderson <kevin.anderso@gmail.com>

---------

Co-authored-by: Kevin Anderson <kevin.anderso@gmail.com>

Author: AdamRJensen

docs/sphinx/source/whatsnew/v0.12.1.rst

@@ -15,6 +15,9 @@ Breaking Changes
   :py:func:`~pvlib.iotools.get_pvgis_tmy` now return ``(data,meta)``
   following the iotools convention instead of ``(data,months_selected,inputs,meta)``.
   (:pull:`2470`)
+* :py:func:`~pvlib.iotools.get_pvgis_tmy` now defaults to ``coerce_year=1990``,
+  whereas the default behavior previously was to use the years of the selected
+  months for the TMY index. (:pull:`2474`)
 * Remove ``outputformat='basic'`` option in :py:func:`~pvlib.iotools.get_pvgis_tmy`.
   (:pull:`2416`)
 

pvlib/iotools/pvgis.py

@@ -434,7 +434,7 @@ def _coerce_and_roll_tmy(tmy_data, tz, year):
 def get_pvgis_tmy(latitude, longitude, outputformat='json', usehorizon=True,
                   userhorizon=None, startyear=None, endyear=None,
                   map_variables=True, url=URL, timeout=30,
-                  roll_utc_offset=None, coerce_year=None):
+                  roll_utc_offset=None, coerce_year=1990):
     """
     Get TMY data from PVGIS.
 
@@ -477,9 +477,11 @@ def get_pvgis_tmy(latitude, longitude, outputformat='json', usehorizon=True,
         Use to specify a time zone other than the default UTC zero and roll
         dataframe by ``roll_utc_offset`` so it starts at midnight on January
         1st. Ignored if ``None``, otherwise will force year to ``coerce_year``.
-    coerce_year: int, optional
-        Use to force indices to desired year. Will default to 1990 if
-        ``coerce_year`` is not specified, but ``roll_utc_offset`` is specified.
+    coerce_year: int, default 1990
+        Use to force indices to desired year. Defaults to 1990. Specify
+        ``None`` to return the actual indices used for the TMY. If
+        ``coerce_year`` is ``None``, but ``roll_utc_offset`` is specified,
+        then ``coerce_year`` will be set to the default.
 
     Returns
     -------

tests/iotools/test_pvgis.py

@@ -384,7 +384,7 @@ def pvgis_tmy_mapped_columns():
 @pytest.mark.flaky(reruns=RERUNS, reruns_delay=RERUNS_DELAY)
 def test_get_pvgis_tmy(expected, month_year_expected, inputs_expected,
                        meta_expected):
-    pvgis_data = get_pvgis_tmy(45, 8, map_variables=False)
+    pvgis_data = get_pvgis_tmy(45, 8, map_variables=False, coerce_year=None)
     _compare_pvgis_tmy_json(expected, month_year_expected, inputs_expected,
                             meta_expected, pvgis_data)
 
@@ -428,7 +428,8 @@ def test_get_pvgis_tmy_kwargs(userhorizon_expected):
     _, meta = get_pvgis_tmy(45, 8, usehorizon=False, map_variables=False)
     assert meta['inputs']['meteo_data']['use_horizon'] is False
     data, _ = get_pvgis_tmy(
-        45, 8, userhorizon=[0, 10, 20, 30, 40, 15, 25, 5], map_variables=False)
+        45, 8, userhorizon=[0, 10, 20, 30, 40, 15, 25, 5], map_variables=False,
+        coerce_year=None)
     assert np.allclose(
         data['G(h)'], userhorizon_expected['G(h)'].values)
     assert np.allclose(
@@ -486,13 +487,17 @@ def test_get_pvgis_tmy_coerce_year():
     for m, test_case in enumerate(noon_test_data):
         expected = pvgis_data[pvgis_data.index.month == m+1].iloc[12]
         assert all(test_case == expected)
+    # Test that get_pvgis_tmy defaults to coerce_year=1990
+    pvgis_data, _ = get_pvgis_tmy(45, 8)
+    assert all(pvgis_data.index.year == 1990)
 
 
 @pytest.mark.remote_data
 @pytest.mark.flaky(reruns=RERUNS, reruns_delay=RERUNS_DELAY)
 def test_get_pvgis_tmy_csv(expected, month_year_expected, inputs_expected,
-                           meta_expected, csv_meta):
-    pvgis_data = get_pvgis_tmy(45, 8, outputformat='csv', map_variables=False)
+                           meta_expected, csv_meta, coerce_year=None):
+    pvgis_data = get_pvgis_tmy(45, 8, outputformat='csv', map_variables=False,
+                               coerce_year=None)
     _compare_pvgis_tmy_csv(expected, month_year_expected, inputs_expected,
                            meta_expected, csv_meta, pvgis_data)
 
@@ -532,7 +537,8 @@ def _compare_pvgis_tmy_csv(expected, month_year_expected, inputs_expected,
 @pytest.mark.remote_data
 @pytest.mark.flaky(reruns=RERUNS, reruns_delay=RERUNS_DELAY)
 def test_get_pvgis_tmy_epw(expected, epw_meta):
-    pvgis_data = get_pvgis_tmy(45, 8, outputformat='epw', map_variables=False)
+    pvgis_data = get_pvgis_tmy(45, 8, outputformat='epw', map_variables=False,
+                               coerce_year=None)
     _compare_pvgis_tmy_epw(expected, epw_meta, pvgis_data)