python road day8

1. Dynamically import modules

lib = __import__("lib.aa") 
c = lib.aa.C() 
print(c.name) 
print(lib.aa.C) #The 

following is the commonly used method 
import importlib 
lib = importlib.import_module('lib. aa') 
print(lib.C()) 


2. The assertion 
is followed by a condition. If it is true, the following program will be executed. If not, an exception will be reported 
. Example 1: 

assert 6 == 6 
print('6 equals 6') 
There is no problem with the appeal, so the following content will be printed 

Example 2:

assert type(2) is str 
print('g is str') 
The assertion in the above example does not hold, so an error will be reported

Traceback (most recent call last):
File "/Users/luobiao/PycharmProjects/s14/day7/lib/aa.py", line 24, in <module>
assert type(2) is str
AssertionError

3. Write a simple socketssh client 
1) server-side code

import socket,os,time #Declare 

socket 
server = socket.socket() #Bind 
ip 
server.bind(('localhost',6767)) 
#Listen 
server.listen () #Wait 
in a loop, and receive connections and Connection address 

while True: 
    conn,addr = server.accept() 
    print(conn,addr) 
    while True: #Receive 
        data 
        data = conn.recv(1024) #Print 
        data and decode 
        print(data.decode() ) #Call 
        the popen module of os and call the command 
        d = os.popen(data.decode()).read() 
        length = str(len(d.encode())) 
        if len(d) == 0: 
            d = 'Command error, please re-enter.' #Return 
        message 
        conn.send(length.encode(encoding='utf-8'))
        #The information sent twice by the socket sticky packet will be stuck together, resulting in an error in reception 
        #Solution 1: Use sleep to sleep for 0.5 seconds, let the buffer time out so that the two data are not in the same buffer 
        #time.sleep(0.5) 
        #Solution Scheme 2: 
        client_ack = conn.recv(1024)#Receive a data, let the client return information 
        print(client_ack.decode()) 
        conn.send(d.encode(encoding='utf-8')) 

server.close( ) 

2) Client code

import socket #Declare 

socket 
client = socket.socket() #Specify the 
connection address and port 
client.connect(('localhost',6060)) #Send 

the message in a loop 
while True: #Let 
    the user enter information, imitating ssh input 
    message = input ('>>: ') #Send 
    a message, convert the data of type str to bytes, and use encode to convert 
    client.send(message.encode(encoding='utf-8')) #Receive 
    the message, and specify the maximum received The amount of data, in bytes 
    length = client.recv(1024).decode() 
    client.send('received size'.encode(encoding='utf-8')) 
    print(length) #Print 
    the message and convert it code 
    #print(length.decode()) 
    recevied_size = 0 
    while int(length)> recevied_size: 
        data = client.recv(1024) 
        recevied_size +=len(data.decode())
        print(data.decode()) 
        print(recevied_size) 
    else: 
        print('Received') #Close 
the link 
client.close()