python string前加b的原因

From：https://stackoverflow.com/questions/6269765/what-does-the-b-character-do-in-front-of-a-string-literal

 they produce an instance of the bytes type instead of the str type. 

 

• str = '...' literals = a sequence of Unicode characters (UTF-16 or UTF-32, depending on how Python was compiled)
• bytes = b'...' literals = a sequence of octets (integers between 0 and 255)

其实也可以加r：代表raw string，不会对转义符' \'进行转义。