python字符串str和字节数组相互转化方法

实例如下：

# bytes object 
b = b"example" 

# str object 
s = "example" 

# str to bytes 
bytes(s, encoding = "utf8") 

# bytes to str 
str(b, encoding = "utf-8") 

# an alternative method 
# str to bytes 
str.encode(s) 

# bytes to str 
bytes.decode(b)