Use simpler dict.get() rather than try/except

rest_framework/fields.py

@@ -1042,16 +1042,10 @@ class ChoiceField(Field):
         except KeyError:
             self.fail('invalid_choice', input=data)
 
-    def representation_value(self, value):
-        try:
-            return self.choice_strings_to_values[six.text_type(value)]
-        except KeyError:
-            return value
-
     def to_representation(self, value):
         if value in ('', None):
             return value
-        return self.representation_value(value)
+        return self.choice_strings_to_values.get(six.text_type(value), value)
 
 
 class MultipleChoiceField(ChoiceField):
@@ -1079,7 +1073,7 @@ class MultipleChoiceField(ChoiceField):
 
     def to_representation(self, value):
         return set([
-            self.representation_value(item) for item in value
+            self.choice_strings_to_values.get(six.text_type(item), item) for item in value
         ])