Print usage if no arguments are provided

dxf_to_csv/dxf_to_csv.py

@@ -122,9 +122,14 @@ def main():
         '-n', metavar='LAYER_NAME', help='name of layer', default=None)
     parser.add_argument(
         '-l', action='store_true', help='show list of layers', default=False)
-    args = parser.parse_args()
+
+    # List usage if no arguments are provided
+    if len(sys.argv) == 1:
+        parser.print_help(sys.stderr)
+        sys.exit(1)
 
     # Parse arguments
+    args = parser.parse_args()
     dxf_name = args.dxf_name
     layer_name = args.n
     show_layers_only = args.l