Fix linting issues in gen_thermochem.py

- Move imports to top-level to fix import-outside-toplevel warnings
- Remove trailing whitespace
- Remove trailing newlines
- Add docstring to main() function
- Add encoding parameter to file open call
- Rename exception variable from 'e' to 'exc'

Pylint now rates the script at 10.00/10.

Author: sbryngelson

toolchain/scripts/gen_thermochem.py

@@ -8,7 +8,22 @@
 import argparse
 import sys
 
+try:
+    import cantera as ct
+except ImportError as exc:
+    print("ERROR: cantera Python package is required for chemistry.", file=sys.stderr)
+    print("Install it with: pip install cantera", file=sys.stderr)
+    raise ImportError("cantera is required for chemistry code generation") from exc
+
+try:
+    import pyrometheus as pyro
+except ImportError as exc:
+    print("ERROR: pyrometheus Python package is required for chemistry.", file=sys.stderr)
+    print("Install it with: pip install pyrometheus", file=sys.stderr)
+    raise ImportError("pyrometheus is required for chemistry code generation") from exc
+
 def main():
+    """Generate m_thermochem.f90 using Pyrometheus and Cantera."""
     parser = argparse.ArgumentParser(
         description="Generate Fortran thermochemistry module via Pyrometheus"
     )
@@ -21,46 +36,31 @@ def main():
     )
     args = parser.parse_args()
 
-    try:
-        import cantera as ct
-    except ImportError:
-        print("ERROR: cantera Python package is required for chemistry.", file=sys.stderr)
-        print("Install it with: pip install cantera", file=sys.stderr)
-        sys.exit(1)
-
-    try:
-        import pyrometheus as pyro
-    except ImportError:
-        print("ERROR: pyrometheus Python package is required for chemistry.", file=sys.stderr)
-        print("Install it with: pip install pyrometheus", file=sys.stderr)
-        sys.exit(1)
-
     # Load the Cantera solution
     # If no mechanism file is specified or it's empty, use Cantera's default h2o2.yaml
     mech_file = args.mech if args.mech else "h2o2.yaml"
-    
+
     try:
         sol = ct.Solution(mech_file)
-    except Exception as e:
-        print(f"ERROR: Failed to load Cantera mechanism '{mech_file}': {e}", file=sys.stderr)
+    except Exception as exc:
+        print(f"ERROR: Failed to load Cantera mechanism '{mech_file}': {exc}", file=sys.stderr)
         sys.exit(1)
 
     # Generate Fortran code using Pyrometheus
     try:
         code = pyro.FortranCodeGenerator().generate(args.module, sol)
-    except Exception as e:
-        print(f"ERROR: Failed to generate Fortran code: {e}", file=sys.stderr)
+    except Exception as exc:
+        print(f"ERROR: Failed to generate Fortran code: {exc}", file=sys.stderr)
         sys.exit(1)
 
     # Write to output file
     try:
-        with open(args.out, 'w') as f:
+        with open(args.out, 'w', encoding='utf-8') as f:
             f.write(code)
         print(f"Successfully generated {args.out} from {mech_file}")
-    except Exception as e:
-        print(f"ERROR: Failed to write output file '{args.out}': {e}", file=sys.stderr)
+    except Exception as exc:
+        print(f"ERROR: Failed to write output file '{args.out}': {exc}", file=sys.stderr)
         sys.exit(1)
 
 if __name__ == "__main__":
     main()
-