mc.losses to mc.results.losses (#1231)

Author: wholmgren

docs/sphinx/source/whatsnew/v0.9.0.rst

@@ -46,7 +46,7 @@ Breaking changes
   :py:func:`pvlib.modelchain.basic_chain` (:issue:`1028`, :pull:`1181`)
 
 * Removed the ``**kwargs`` parameters from :py:meth:`~pvlib.pvsystem.PVSystem.sapm` and
-  :py:meth:`~pvlib.pvsystem.PVSystem.calcparams_desoto` and 
+  :py:meth:`~pvlib.pvsystem.PVSystem.calcparams_desoto` and
   :py:meth:`~pvlib.pvsystem.PVSystem.calcparams_cec` (:issue:`1118`, :pull:`1222`)
 
 
@@ -64,6 +64,7 @@ Deprecations
   * ``ModelChain.dc``
   * ``ModelChain.diode_params``
   * ``ModelChain.effective_irradiance``
+  * ``ModelChain.losses``
   * ``ModelChain.solar_position``
   * ``ModelChain.spectral_modifier``
   * ``ModelChain.total_irrad``

pvlib/modelchain.py

@@ -277,6 +277,7 @@ class ModelChainResult:
         field(default=None)
     diode_params: Optional[PerArray[pd.DataFrame]] = field(default=None)
     dc_ohmic_losses: Optional[PerArray[pd.Series]] = field(default=None)
+    losses: Optional[Union[pd.Series, float]] = field(default=None)
 
     weather: Optional[PerArray[pd.DataFrame]] = None
     times: Optional[pd.DatetimeIndex] = None
@@ -379,7 +380,7 @@ class ModelChain:
                          'aoi', 'aoi_modifier', 'spectral_modifier',
                          'cell_temperature', 'effective_irradiance',
                          'dc', 'ac', 'diode_params', 'tracking',
-                         'weather', 'times']
+                         'weather', 'times', 'losses']
 
     def __init__(self, system, location,
                  clearsky_model='ineichen',
@@ -1094,16 +1095,16 @@ def infer_losses_model(self):
         raise NotImplementedError
 
     def pvwatts_losses(self):
-        self.losses = (100 - self.system.pvwatts_losses()) / 100.
+        self.results.losses = (100 - self.system.pvwatts_losses()) / 100.
         if isinstance(self.results.dc, tuple):
             for dc in self.results.dc:
-                dc *= self.losses
+                dc *= self.results.losses
         else:
-            self.results.dc *= self.losses
+            self.results.dc *= self.results.losses
         return self
 
     def no_extra_losses(self):
-        self.losses = 1
+        self.results.losses = 1
         return self
 
     def effective_irradiance_model(self):

pvlib/tests/test_modelchain.py

@@ -1542,8 +1542,8 @@ def test_spectral_models_singleton_weather_single_array(
 
 
 def constant_losses(mc):
-    mc.losses = 0.9
-    mc.results.dc *= mc.losses
+    mc.results.losses = 0.9
+    mc.results.dc *= mc.results.losses
 
 
 def dc_constant_losses(mc):
@@ -1682,7 +1682,7 @@ def test_losses_models_ext_def(pvwatts_dc_pvwatts_ac_system, location, weather,
     mc.run_model(weather)
     assert m.call_count == 1
     assert isinstance(mc.results.ac, (pd.Series, pd.DataFrame))
-    assert mc.losses == 0.9
+    assert mc.results.losses == 0.9
     assert not mc.results.ac.empty
 
 
@@ -1695,7 +1695,7 @@ def test_losses_models_no_loss(pvwatts_dc_pvwatts_ac_system, location, weather,
     assert mc.losses_model == mc.no_extra_losses
     mc.run_model(weather)
     assert m.call_count == 0
-    assert mc.losses == 1
+    assert mc.results.losses == 1
 
 
 def test_invalid_dc_model_params(sapm_dc_snl_ac_system, cec_dc_snl_ac_system,