refactor error handling of invalid SMILES

ChemID.py

@@ -18,29 +18,32 @@ def ResolveChemical(chemName, IDtype):
 
     if IDtype == 'CAS':
         cas = chemName
-        if not is_cas(cas):
-            name = 'INVALID CAS'
-            error = 3
-            return (name, cas, None, None, None, error)
         smiles = None
         name = None
         Mw = None
         im64 = None
         error = 0
 
+        if not is_cas(cas):
+            error = 3 #invalid cas
+            return (name, cas, smiles, Mw, im64, error)
+
         smiles = cas2smiles(cas)
 
         if smiles:
             name = cas2name(cas)
             try:
                 mol = Chem.MolFromSmiles(smiles)
+            except:
+                error = 2 #invalid smiles
+            if mol:
                 Mw = Descriptors.MolWt(mol)
                 im = ImageFromSmiles(smiles)
                 im64 = Imageto64(im)
-            except:
-                error = 2
+            else:
+                error = 2 #invalid smiles
         else:
-            error = 1
+            error = 1 # no smiles found
     elif IDtype == 'SMILES':
         smiles = chemName
         cas = None
@@ -55,10 +58,13 @@ def ResolveChemical(chemName, IDtype):
 
         try:
             mol = Chem.MolFromSmiles(smiles)
+        except:
+            error = 2
+        if mol:
             Mw = Descriptors.MolWt(mol)
             im = ImageFromSmiles(smiles)
             im64 = Imageto64(im)
-        except:
+        else:
             error = 2
     elif IDtype == 'common':
         name = chemName
@@ -74,10 +80,13 @@ def ResolveChemical(chemName, IDtype):
             cas = name2cas(name)
             try:
                 mol = Chem.MolFromSmiles(smiles)
+            except:
+                error = 2
+            if mol:
                 Mw = Descriptors.MolWt(mol)
                 im = ImageFromSmiles(smiles)
                 im64 = Imageto64(im)
-            except:
+            else:
                 error = 2
         else:
             error = 1
@@ -88,7 +97,7 @@ def ResolveChemical(chemName, IDtype):
         cas = None
         Mw = None
         im64 = None
-        error = 4
+        error = 4 # invalid IDtype selection, probably not possible
 
     # if we couldn't find a name or CAS (but do have SMILES)
     if not error: