[pyassimp] Check cmd line args in sample.py

port/PyAssimp/scripts/sample.py

@@ -77,5 +77,12 @@ def main(filename=None):
     # Finally release the model
     pyassimp.release(scene)
 
+def usage():
+    print("Usage: sample.py <3d model>")
+
 if __name__ == "__main__":
-    main(sys.argv[1] if len(sys.argv)>1 else None)
+
+    if len(sys.argv) != 2:
+        usage()
+    else:
+        main(sys.argv[1])