improve function argument ordering in pvsystem (#220)

* make more pvsystem functions less pandas centric

* update tests

* change snlinverter api. update whatsnew

* fix bad rebase in tools

* add test decorators

* reorder sapm function arguments

* fix pre-python 3.5 syntax error in test

Author: wholmgren

docs/sphinx/source/package_overview.rst

@@ -105,10 +105,10 @@ to accomplish our system modeling goal:
         temps = pvlib.pvsystem.sapm_celltemp(total_irrad['poa_global'],
                                              wind_speed, temp_air)
         effective_irradiance = pvlib.pvsystem.sapm_effective_irradiance(
-            module, total_irrad['poa_direct'], total_irrad['poa_diffuse'],
-            am_abs, aoi)
-        dc = pvlib.pvsystem.sapm(module, effective_irradiance, temps['temp_cell'])
-        ac = pvlib.pvsystem.snlinverter(inverter, dc['v_mp'], dc['p_mp'])
+            total_irrad['poa_direct'], total_irrad['poa_diffuse'],
+            am_abs, aoi, module)
+        dc = pvlib.pvsystem.sapm(effective_irradiance, temps['temp_cell'], module)
+        ac = pvlib.pvsystem.snlinverter(dc['v_mp'], dc['p_mp'], inverter)
         annual_energy = ac.sum()
         energies[name] = annual_energy
 

docs/sphinx/source/whatsnew/v0.4.0.txt

@@ -19,6 +19,9 @@ API Changes
   in addition to arrays and Series. Furthermore, these functions no
   longer promote scalar or array input to Series output.
   Also applies to atmosphere.relativeairmass. (:issue:`201`, :issue:`214`)
+* Reorder the ashraeiam, physicaliam, and snlinverter arguments to put
+  the most variable arguments first. Adds default arguments for the IAM
+  functions. (:issue:`197`)
 * The irradiance.extraradiation function input/output type consistency
   across different methods has been dramatically improved.
   (:issue:`217`, :issue:`219`)

pvlib/modelchain.py

@@ -170,13 +170,13 @@ def basic_chain(times, latitude, longitude,
                                    weather['temp_air'])
 
     effective_irradiance = pvsystem.sapm_effective_irradiance(
-        module_parameters, total_irrad['poa_direct'],
-        total_irrad['poa_diffuse'], airmass, aoi)
+        total_irrad['poa_direct'], total_irrad['poa_diffuse'], airmass, aoi,
+        module_parameters)
 
-    dc = pvsystem.sapm(module_parameters, effective_irradiance,
-                       temps['temp_cell'])
+    dc = pvsystem.sapm(effective_irradiance, temps['temp_cell'],
+                       module_parameters)
 
-    ac = pvsystem.snlinverter(inverter_parameters, dc['v_mp'], dc['p_mp'])
+    ac = pvsystem.snlinverter(dc['v_mp'], dc['p_mp'], inverter_parameters)
 
     return dc, ac