telnetlib_test.py

from telnetlib import Telnet
from sys import stdin, stdout
from collections import deque


class TelnetClient():
    def __init__(self, addr, port=23):
        self.addr = addr
        self.port = port
        self.tn = None

    def start(self):
        # user
        t = self.tn.read_until('login: ')
        stdout.write(t)
        user = stdin.readline()
        self.tn.write(user)

        # password
        t = self.tn.read_until('Password: ')
        if t.startswith(user[:-1]):
            t = t[len(user) + 1:]
        stdout.write(t)
        self.tn.write(stdin.readline())

        t = self.tn.read_until('$ ')
        stdout.writ(t)
        while 1:
            uinput = stdin.readline()
            if not uinput:
                break
            self.history.append(uinput)
            self.tn.write(uinput)
            t = self.tn.read_until('$ ')
            stdout.write(t[len(uinput) + 1:])

    def __enter__(self):
        self.tn = Telnet(self.addr, self.port)
        self.history = deque()
        # here the `self` will be passed to the variable after `as` -> 'clinet'
        return self 

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.tn.close()
        self.tn = None
        with open(self.addr + 'history.txt', 'a') as f:
            f.writelines(self.history)


with TelnetClient('127.0.0.1') as clinet:  
# the client is the `self` __enter__ returned
    client.start()