week8

---恢复内容开始---

week8

1、动态导入模块

2、断言

3、ftp

4、socketserver

1、动态导入模块

 import importlib
 a = importlib.import_module('aa.aa') # aa目录下的aa模块
 print(aa.import_C().name)

2、断言

跟if有点类似，判断是否符合条件，是则继续，否则报错。

 a = 'name'
 assert type(a) is str

3、FTP(文件传输：单下载)

 客户端
 1、读取文件名
 2、检测文件是否存在
 3、打开文件
 4、检测文件大小
 5、发送文件大小给客户端
 6、客户端确认
 7、开始边读边发数据
 8、md5

 import socket,os,hashlib
 server = socket.socket()
 server.bind(('localhost',9999))
 server.lisen()
 m = hashlib.md5()
 while True:
     try:
         conn,addr = server.accept()
         data = conn.recv(1024)
         cmd,filename =data.split()
         if os.path.isfile(filename):
             f = open(filename,'rb')
             filesize = f.stat(filename).st_size
             conn.send(str(filesize).encode())
             conn.recv(1024)
             for line in f:
                 m.update(line)
                 conn.send(line)
                 print(m.hexdigest())
             conn.send(str(hexdigest).encode)
             f.close
         print(send done')
     except ConnectionResetError as e:
         print('连接错误',e)
 server.close()

客户端

 import socket,os,hashlib
 client = socket.socket()
 client.connect(('localhost',9999))
 m = hashlib.md5
 while True:
     cmd = imput('>>>:').strip()
     if len(cmd) == 0:continue
     filesize = client.recv(1024)
     client.send('请求发送’) #无实际意义的交互，防止粘包
     filename = cmd.split[1]
     f = open(filename+'.new','wb')
     rec_filesize = 0
     filesize = int(filesize.decode())
     while filesize > rec_filesize:
         if filesize - rec_filesize > 1024: # 做判断防止最后一次接收出现粘包
             res_size = 1024
         else:
             res_size = filesize - rec_filesize
         data = client.recv(res_size)
         f.write(data)
         rec_filesize += len(data)
         m.update(data)
     else:
         new_file_md5 = m.hexdigest()
         print('new file md5:',new_file_md5)
     server_file_md5 = client.recv(1024)
     print('server file md5',server_file_md5) #接收服务端读取的md5，与自己生成的md5进行比较
 client.close

服务端

4、socketserver(面向对象的方法进行文件传输)

创建方式:

创建一个socketserver 至少分以下几步:

First, you must create a request handler class by subclassing the BaseRequestHandlerclass and overriding its handle() method; this method will process incoming requests. 　　
Second, you must instantiate one of the server classes, passing it the server’s address and the request handler class.
Then call the handle_request() orserve_forever() method of the server object to process one or many requests.
Finally, call server_close() to close the socket.

self.setup  请求处理前进行的事项
self.handle 请求处理中的事项
self.finish 请求处理后的事项

 import socketserver

 class MyTCPServer(socketserver.BaseRequestHandler):
     def setup(self): #交互前的动作
         pass
     def handle(self): #与用户的所有交互都在这里进行
         self.data = self.request.recv(1024)
         print("{} wrote:".format(self.client_address[0]))
         self.request.sendall(self.data.upper)
     def finish(self): #与用户交互后的动作
         pass

 if  __name__ == '__main__'
     HOST , PORT = 'localhost',9999
     server = socketserver.ThreadingTCPServer((HOST,PORT),MyTCPServer)
 #ThreadingTCPServer 多线程
 #ForingTCPServer 多进程 在win不好使
 server.server_forever()

客户端