MAINT rework if/else construct, add comments

smac/facade/smac_facade.py

@@ -113,18 +113,23 @@ def __init__(self,
                                    scenario.cs)
 
         # initialize tae_runner
-        if tae_runner is not None and callable(tae_runner):
-            tae_runner = ExecuteTAFunc(ta=tae_runner,
-                                       stats=self.stats,
-                                       run_obj=scenario.run_obj,
-                                       runhistory=runhistory,
-                                       par_factor=scenario.par_factor)
-        elif tae_runner is None:
+        # First case, if tae_runner is None, the target algorithm is a call
+        # string in the scenario file
+        if tae_runner is None:
             tae_runner = ExecuteTARunOld(ta=scenario.ta,
                                          stats=self.stats,
                                          run_obj=scenario.run_obj,
                                          runhistory=runhistory,
                                          par_factor=scenario.par_factor)
+        # Second case, the tae_runner is a function to be optimized
+        elif callable(tae_runner):
+            tae_runner = ExecuteTAFunc(ta=tae_runner,
+                                       stats=self.stats,
+                                       run_obj=scenario.run_obj,
+                                       runhistory=runhistory,
+                                       par_factor=scenario.par_factor)
+        # Third case, if it is an ExecuteTaRun we can simply use the
+        # instance. Otherwise, the next check raises an exception
         elif not isinstance(tae_runner, ExecuteTARun):
             raise TypeError("Argument 'tae_runner' is %s, but must be "
                             "either a callable or an instance of "