Check ensemble identifiers.

climax/main/preprocess.py

@@ -54,14 +54,15 @@ if __name__ == '__main__':
             args.target.mkdir(parents=True, exist_ok=True)
 
         # check ensemble identifier
-        ensemble_pattern = 'r[0-9]i[0-9]p[0-9]'
-        ensemble = re.search(ensemble_pattern, args.ensemble)
-        if ensemble is None:
-            LOGGER.info('Ensemble identifier "{}" invalid, form "{}" required.'
-                        .format(args.ensemble, ensemble_pattern))
-            sys.exit()
-        else:
-            ensemble = ensemble[0]
+        if args.ensemble is not None:
+            ensemble_id = 'r[0-9]i[0-9]p[0-9]'
+            ensemble = re.search(ensemble_id, args.ensemble)
+            if ensemble is None:
+                LOGGER.info('Ensemble identifier "{}" invalid, form "{}" '
+                            'required.'.format(args.ensemble, ensemble_id))
+                sys.exit()
+            else:
+                ensemble = ensemble[0]
 
         # construct file pattern to match from input parameters
         pattern = '(.*).nc$'