with open("yesterday","r") as f，\

    open("yesterday2","r") as f2: 同时打开两个文件

    for line in f :

        print(line)

当with代码块执行完毕时，内部会自动关闭并释放文件资源。

字符编码：

Unicode    包含GBK和UTF-8

Unicode encode 编码码成UTF-8   encode编码码成GBK

UTF-8 和GBK decode 编码成 Unicode

s="你好"

print(s.encode("gbk"))  把s编码成GBK  

s_to_gbk = s.decode("utf-8").encode("gbk")

print(s.encode("utf-8").decode("utf-8").encode("gb2312").decode("gb2312")）

            编码成utf-8，解码成Unicode    再编码成gb2312   再解码gb2312成Unicode

34.字符编码