Minor improvements to yaml dumping for ArkaneSpecies

Provide file stream directly to yaml.dump
Remove optional Dumper argument and associated imports
Add str representer to dump multiline strings as block literals

arkane/common.py

@@ -35,10 +35,6 @@
 import string
 
 import yaml
-try:
-    from yaml import CDumper as Dumper, CLoader as Loader, CSafeLoader as SafeLoader
-except ImportError:
-    from yaml import Dumper, Loader, SafeLoader
 
 from rmgpy.rmgobject import RMGObject
 from rmgpy import __version__
@@ -61,6 +57,16 @@
 ################################################################################
 
 
+# Add a custom string representer to use block literals for multiline strings
+def str_repr(dumper, data):
+    if len(data.splitlines()) > 1:
+        return dumper.represent_scalar('tag:yaml.org,2002:str', data, style='|')
+    return dumper.represent_scalar('tag:yaml.org,2002:str', data)
+
+
+yaml.add_representer(str, str_repr)
+
+
 class ArkaneSpecies(RMGObject):
     """
     A class for archiving an Arkane species including its statmech data into .yml files
@@ -206,7 +212,7 @@ def save_yaml(self, path):
                                 ''.join(c for c in self.label if c in valid_chars) + '.yml')
         full_path = os.path.join(path, filename)
         with open(full_path, 'w') as f:
-            f.write(yaml.dump(data=self.as_dict(), Dumper=Dumper))
+            yaml.dump(data=self.as_dict(), stream=f)
         logging.debug('Dumping species {0} data as {1}'.format(self.label, filename))
 
     def load_yaml(self, path, species, pdep=False):