sys.argv command line parameter list, the first element is the path of the program itself sys.exit(n) exit the program, exit(0) when exiting normally sys.version Get the version information of the Python interpreter sys.maxint maximum Int value sys.path returns the search path of the module, using the value of the PYTHONPATH environment variable during initialization sys.platform returns the OS platform name sys.stdout.write('please:') val = sys.stdin.readline()[:-1]