true exemple of -X dev option

exemples.py

-#######  CONTEXTE  ###########
 
 # python -X dev
-# from threading import Thread
+# import sys
 
-# thread = Thread()
-# thread.isAlive()
+# def main():
+#     fp = open('README.md')
+#     nlines = len(fp.readlines())
+#     print(nlines)
+#     # The file is closed implicitly
+
+# if __name__ == "__main__":
+#     main()
 
 # name == main
 # from mauvais_module import fonction_utile1