000-- the way to define a string with several lines
001--to get specific letters from a string
002-- the common error message for new beginner while running python script
http://www.cnblogs.com/smile-ls/archive/2013/05/20/3088393.html
003-- check the security of the password
004-- open a file with the path in the computer:
005-- the commen functions for Strings:
http://www.cnblogs.com/huangcong/archive/2011/08/29/2158268.html