diff --git a/lems/run.py b/lems/run.py
index 1d2807f..2aaeb99 100644
--- a/lems/run.py
+++ b/lems/run.py
@@ -41,12 +41,25 @@ def process_args():
     
     return parser.parse_args()
 
-def main():
+def run(file_path,include_dirs=[],dlems=False,nogui=False):
+    """
+    Function for running from a script or shell.
+    """
+    import argparse
+    args = argparse.Namespace()
+    args.lems_file = file_path
+    args.I = include_dirs
+    args.dlems = dlems
+    args.nogui = nogui
+    main(args=args)
+
+def main(args=None):
     """
     Program entry point.
     """
     
-    args = process_args()
+    if args is None:
+        args = process_args()
     
     print('Parsing and resolving model: '+args.lems_file)
     model = Model()
diff --git a/lems/sim/runnable.py b/lems/sim/runnable.py
index f67d4a4..6f8dc1f 100644
--- a/lems/sim/runnable.py
+++ b/lems/sim/runnable.py
@@ -187,6 +187,9 @@ def add_child_to_group(self, group_name, child):
         #print sorted(self.__dict__.keys())
         #print ".........."
         #print self.__dict__[group_name]
+        # Force group_name attribute to be a list before we append to it.
+        if type(self.__dict__[group_name]) is not list:
+            self.__dict__[group_name] = [self.__dict__[group_name]]
         self.__dict__[group_name].append(child)
         child.parent = self