Our first Expect program

Our first program extends what we have done in the last section with some additional code:

     #!/usr/bin/python3

     import pexpect

     devices = {'iosv-1': {'prompt': 'iosv-1#', 'ip': '172.16.1.20'}, 'iosv-2': {'prompt': 'iosv-2#', 'ip': '172.16.1.21'}}
     username = 'cisco'
     password = 'cisco'

     for device in devices.keys():
         device_prompt = devices[device]['prompt']
         child = pexpect.spawn('telnet ' + devices[device]['ip'])
         child.expect('Username:')
         child.sendline(username)
         child.expect('Password:')
         child.sendline(password)
         child.expect(device_prompt)
         child.sendline('show version | i V')
         child.expect(device_prompt)
         print(child.before)
         child.sendline('exit')

We use a nested dictionary in line 5:

       devices = {'iosv-1': {'prompt': 'iosv-1#', 'ip': 
      '172.16.1.20'}, 'iosv-2': {'prompt': 'iosv-2#', 
      'ip': '172.16.1.21'}}

The nested dictionary allows us to refer to the same device (such as iosv-1) with the appropriate IP address and prompt symbol. We can then use those values for the expect() method later on in the loop.

The output prints out the 'show version | i V' output on the screen for each of the devices:

    $ python3 chapter2_1.py
      b'show version | i VrnCisco IOS Software, IOSv
      Software (VIOS-ADVENTERPRISEK9-M), Version 15.6(2)T, 
    RELEASE SOFTWARE (fc2)rnProcessor board ID 
    9MM4BI7B0DSWK40KV1IIRrn'
    b'show version | i VrnCisco IOS Software, IOSv 
    Software (VIOS-ADVENTERPRISEK9-M), Version 15.6(2)T,
     RELEASE SOFTWARE (fc2)rn'