diff --git a/interfaces/cython/cantera/ctml2yaml.py b/interfaces/cython/cantera/ctml2yaml.py
index 94b1d30eb68..316b367725c 100644
--- a/interfaces/cython/cantera/ctml2yaml.py
+++ b/interfaces/cython/cantera/ctml2yaml.py
@@ -9,6 +9,8 @@
 import xml.etree.ElementTree as etree
 from email.utils import formatdate
 
+from typing import Any
+
 try:
     import ruamel_yaml as yaml
 except ImportError:
@@ -31,25 +33,23 @@ def FlowList(*args, **kwargs):
 
 
 # Improved float formatting requires Numpy >= 1.14
-if hasattr(np, "format_float_positional"):
-
-    def float2string(data):
-        if data == 0:
-            return "0.0"
-        elif 0.01 <= abs(data) < 10000:
-            return np.format_float_positional(data, trim="0")
-        else:
-            return np.format_float_scientific(data, trim="0")
+HAS_FMT_FLT_POS = hasattr(np, "format_float_positional")
 
 
-else:
-
-    def float2string(data):
+def float2string(data):
+    if not HAS_FMT_FLT_POS:
         return repr(data)
 
+    if data == 0:
+        return "0.0"
+    elif 0.01 <= abs(data) < 10000:
+        return np.format_float_positional(data, trim="0")
+    else:
+        return np.format_float_scientific(data, trim="0")
+
 
 def represent_float(self, data):
-    # type: (Any) -> Any
+    # type: (Any, Any) -> Any
     if data != data:
         value = ".nan"
     elif data == self.inf_value:
@@ -648,6 +648,7 @@ def convert(inpfile, outfile):
     for phase_node in ctml_tree.iterfind("phase"):
         this_phase = Phase(phase_node)
         phases.append(this_phase)
+
         reaction_filter = phase_node.find("./reactionArray/include")
         if reaction_filter is not None:
             if reaction_filter.get("min") != reaction_filter.get("max"):
@@ -662,7 +663,6 @@ def convert(inpfile, outfile):
     # Species
     species_data = []
     for species in ctml_tree.find("speciesData").iterfind("species"):
-
         species_data.append(Species(species))
 
     # Reactions
@@ -694,12 +694,10 @@ def convert(inpfile, outfile):
     output_species = BlockMap({"species": species_data})
     output_species.yaml_set_comment_before_after_key("species", before="\n")
 
-    yaml_obj = yaml.YAML()
-    yaml_obj.register_class(Phase)
-    yaml_obj.register_class(Species)
-    yaml_obj.register_class(SpeciesThermo)
-    yaml_obj.register_class(SpeciesTransport)
-    yaml_obj.register_class(Reaction)
+    emitter = yaml.YAML()
+    for cl in [Phase, Species, SpeciesThermo, SpeciesTransport, Reaction]:
+        emitter.register_class(cl)
+
     metadata = BlockMap(
         {
             "generator": "ctml2yaml",
@@ -710,10 +708,10 @@ def convert(inpfile, outfile):
     if inpfile is not None:
         metadata["input-files"] = FlowList([str(inpfile)])
     with Path(outfile).open("w") as output_file:
-        yaml_obj.dump(metadata, output_file)
-        yaml_obj.dump(output_phases, output_file)
-        yaml_obj.dump(output_species, output_file)
-        yaml_obj.dump(output_reactions, output_file)
+        emitter.dump(metadata, output_file)
+        emitter.dump(output_phases, output_file)
+        emitter.dump(output_species, output_file)
+        emitter.dump(output_reactions, output_file)
 
 
 if __name__ == "__main__":