fix(SU2_PY, SU2_CFD): Python 3 compatibility and C++ code quality improvements (#2643)

Python fixes:
- Replace deprecated .iteritems() with .items() in bunch.py,
  ordered_bunch.py
- Replace deprecated .itervalues() with .values() in ordered_dict.py
- Replace keys().sort() with sorted(keys()) in bunch.py as
  dict.keys() returns a view object in Python 3
- Replace unicode type with str in data.py (unicode was merged
  into str in Python 3)
- Replace 'raise StopIteration' with 'return' in switch.py
  (PEP 479: raising StopIteration inside a generator is deprecated
  in Python 3.7+ and causes RuntimeError)

C++ fixes:
- Remove redundant '== true' boolean comparison in
  CSpeciesFlameletSolver.cpp (line 443)

These changes ensure the SU2 Python utilities work correctly with
Python 3.x and improve C++ code quality.

Signed-off-by: shbhmexe <shubhushukla586@gmail.com>

Author: Shubham shukla

SU2_CFD/src/solvers/CSpeciesFlameletSolver.cpp

@@ -440,7 +440,7 @@ void CSpeciesFlameletSolver::BC_Isothermal_Wall_Generic(CGeometry* geometry, CSo
     /*--- Check if the node belongs to the domain (i.e., not a halo node). ---*/
 
     if (geometry->nodes->GetDomain(iPoint)) {
-      if (config->GetMarker_StrongBC(Marker_Tag) == true) {
+      if (config->GetMarker_StrongBC(Marker_Tag)) {
         /*--- Initial guess for enthalpy value. ---*/
         enth_wall = nodes->GetSolution(iPoint, I_ENTH);
 

SU2_PY/SU2/io/data.py

@@ -359,7 +359,7 @@ def rec2dict(array_in):
         value = array_in[key].tolist()[0][0]
 
         # convert string
-        if isinstance(value[0], unicode):
+        if isinstance(value[0], str):
             value = str(value[0])
 
         # convert array

SU2_PY/SU2/util/bunch.py

@@ -194,15 +194,13 @@ def __repr__(self):
 
         (*) Invertible so long as collection contents are each repr-invertible.
         """
-        keys = self.keys()
-        keys.sort()
+        keys = sorted(self.keys())
         args = ", ".join(["%s=%r" % (key, self[key]) for key in keys])
         return "%s(%s)" % (self.__class__.__name__, args)
 
     def __str__(self):
         """String-form of a OrderedBunch."""
-        keys = self.keys()
-        keys.sort()
+        keys = sorted(self.keys())
         args = ", ".join(["%s=%r" % (key, self[key]) for key in keys])
         return "{%s}" % args
 
@@ -247,7 +245,7 @@ def bunchify(x):
     nb. As dicts are not hashable, they cannot be nested in sets/frozensets.
     """
     if isinstance(x, dict):
-        return Bunch((k, bunchify(v)) for k, v in x.iteritems())
+        return Bunch((k, bunchify(v)) for k, v in x.items())
     elif isinstance(x, (list, tuple)):
         return type(x)(bunchify(v) for v in x)
     else:
@@ -273,7 +271,7 @@ def unbunchify(x):
     nb. As dicts are not hashable, they cannot be nested in sets/frozensets.
     """
     if isinstance(x, dict):
-        return dict((k, unbunchify(v)) for k, v in x.iteritems())
+        return dict((k, unbunchify(v)) for k, v in x.items())
     elif isinstance(x, (list, tuple)):
         return type(x)(unbunchify(v) for v in x)
     else:

SU2_PY/SU2/util/ordered_bunch.py

@@ -265,7 +265,7 @@ def ordered_bunchify(x):
     nb. As dicts are not hashable, they cannot be nested in sets/frozensets.
     """
     if isinstance(x, dict):
-        return OrderedBunch((k, ordered_bunchify(v)) for k, v in x.iteritems())
+        return OrderedBunch((k, ordered_bunchify(v)) for k, v in x.items())
     elif isinstance(x, (list, tuple)):
         return type(x)(ordered_bunchify(v) for v in x)
     else:
@@ -291,9 +291,9 @@ def ordered_unbunchify(x):
     nb. As dicts are not hashable, they cannot be nested in sets/frozensets.
     """
     if isinstance(x, OrderedDict):
-        return OrderedDict((k, ordered_unbunchify(v)) for k, v in x.iteritems())
+        return OrderedDict((k, ordered_unbunchify(v)) for k, v in x.items())
     elif isinstance(x, dict):
-        return dict((k, ordered_unbunchify(v)) for k, v in x.iteritems())
+        return dict((k, ordered_unbunchify(v)) for k, v in x.items())
     elif isinstance(x, (list, tuple)):
         return type(x)(ordered_unbunchify(v) for v in x)
     else:

SU2_PY/SU2/util/ordered_dict.py

@@ -85,7 +85,7 @@ def __reversed__(self):
     def clear(self):
         "od.clear() -> None.  Remove all items from od."
         try:
-            for node in self.__map.itervalues():
+            for node in self.__map.values():
                 del node[:]
             root = self.__root
             root[:] = [root, root, None]

SU2_PY/SU2/util/switch.py

@@ -38,7 +38,7 @@ def __init__(self, value):
     def __iter__(self):
         """Return the match method once, then stop"""
         yield self.match
-        raise StopIteration
+        return
 
     def match(self, *args):
         """Indicate whether or not to enter a case suite"""