refactor repeated code in ModelChain singlediode and LocalizedPVSystem init (pvlib#777)

* Remove duplicate code in ModelChain

* Remove duplicate code in init methods

Author: Peque

pvlib/modelchain.py

@@ -453,11 +453,11 @@ def sapm(self):
 
         return self
 
-    def desoto(self):
+    def _singlediode(self, calcparams_model_function):
         (photocurrent, saturation_current, resistance_series,
          resistance_shunt, nNsVth) = (
-            self.system.calcparams_desoto(self.effective_irradiance,
-                                          self.cell_temperature))
+            calcparams_model_function(self.effective_irradiance,
+                                      self.cell_temperature))
 
         self.diode_params = (photocurrent, saturation_current,
                              resistance_series,
@@ -471,41 +471,14 @@ def desoto(self):
 
         return self
 
-    def cec(self):
-        (photocurrent, saturation_current, resistance_series,
-         resistance_shunt, nNsVth) = (
-            self.system.calcparams_cec(self.effective_irradiance,
-                                       self.cell_temperature))
-
-        self.diode_params = (photocurrent, saturation_current,
-                             resistance_series,
-                             resistance_shunt, nNsVth)
-
-        self.dc = self.system.singlediode(
-            photocurrent, saturation_current, resistance_series,
-            resistance_shunt, nNsVth)
-
-        self.dc = self.system.scale_voltage_current_power(self.dc).fillna(0)
+    def desoto(self):
+        return self._singlediode(self.system.calcparams_desoto)
 
-        return self
+    def cec(self):
+        return self._singlediode(self.system.calcparams_cec)
 
     def pvsyst(self):
-        (photocurrent, saturation_current, resistance_series,
-         resistance_shunt, nNsVth) = (
-            self.system.calcparams_pvsyst(self.effective_irradiance,
-                                          self.cell_temperature))
-
-        self.diode_params = (photocurrent, saturation_current,
-                             resistance_series,
-                             resistance_shunt, nNsVth)
-
-        self.dc = self.system.singlediode(
-            photocurrent, saturation_current, resistance_series,
-            resistance_shunt, nNsVth)
-
-        self.dc = self.system.scale_voltage_current_power(self.dc).fillna(0)
-
-        return self
+        return self._singlediode(self.system.calcparams_pvsyst)
 
     def singlediode(self):
         """Deprecated"""

pvlib/pvsystem.py

@@ -45,6 +45,27 @@
 }
 
 
+def _combine_localized_attributes(pvsystem=None, location=None, **kwargs):
+    """
+    Get and combine attributes from the pvsystem and/or location
+    with the rest of the kwargs.
+    """
+    if pvsystem is not None:
+        pv_dict = pvsystem.__dict__
+    else:
+        pv_dict = {}
+
+    if location is not None:
+        loc_dict = location.__dict__
+    else:
+        loc_dict = {}
+
+    new_kwargs = dict(
+        list(pv_dict.items()) + list(loc_dict.items()) + list(kwargs.items())
+    )
+    return new_kwargs
+
+
 # not sure if this belongs in the pvsystem module.
 # maybe something more like core.py? It may eventually grow to
 # import a lot more functionality from other modules.
@@ -830,22 +851,11 @@ class LocalizedPVSystem(PVSystem, Location):
     """
     def __init__(self, pvsystem=None, location=None, **kwargs):
 
-        # get and combine attributes from the pvsystem and/or location
-        # with the rest of the kwargs
-
-        if pvsystem is not None:
-            pv_dict = pvsystem.__dict__
-        else:
-            pv_dict = {}
-
-        if location is not None:
-            loc_dict = location.__dict__
-        else:
-            loc_dict = {}
-
-        new_kwargs = dict(list(pv_dict.items()) +
-                          list(loc_dict.items()) +
-                          list(kwargs.items()))
+        new_kwargs = _combine_localized_attributes(
+            pvsystem=pvsystem,
+            location=location,
+            **kwargs,
+        )
 
         PVSystem.__init__(self, **new_kwargs)
         Location.__init__(self, **new_kwargs)

pvlib/tracking.py

@@ -2,6 +2,7 @@
 import pandas as pd
 
 from pvlib.tools import cosd, sind
+from pvlib.pvsystem import _combine_localized_attributes
 from pvlib.pvsystem import PVSystem
 from pvlib.location import Location
 from pvlib import irradiance, atmosphere
@@ -227,22 +228,11 @@ class LocalizedSingleAxisTracker(SingleAxisTracker, Location):
 
     def __init__(self, pvsystem=None, location=None, **kwargs):
 
-        # get and combine attributes from the pvsystem and/or location
-        # with the rest of the kwargs
-
-        if pvsystem is not None:
-            pv_dict = pvsystem.__dict__
-        else:
-            pv_dict = {}
-
-        if location is not None:
-            loc_dict = location.__dict__
-        else:
-            loc_dict = {}
-
-        new_kwargs = dict(list(pv_dict.items()) +
-                          list(loc_dict.items()) +
-                          list(kwargs.items()))
+        new_kwargs = _combine_localized_attributes(
+            pvsystem=pvsystem,
+            location=location,
+            **kwargs,
+        )
 
         SingleAxisTracker.__init__(self, **new_kwargs)
         Location.__init__(self, **new_kwargs)