More Pexpect features

In this section, we will look at more Pexpect features that might come in handy when certain situations arise.

If you have a slow or fast link to your remote device, the default expect() method timeout is 30 seconds, which can be increased or decreased via the timeout argument:

>>> child.expect('Username', timeout=5)

You can choose to pass the command back to the user using the interact() method. This is useful when you just want to automate certain parts of the initial task:

>>> child.sendline('show version | i V')
19
>>> child.expect('iosv-1#')
0
>>> child.before
b'show version | i VrnCisco IOS Software, IOSv Software (VIOS-ADVENTERPRISEK9-M), Version 15.6(2)T, RELEASE SOFTWARE (fc2)rnProcessor board ID 9MM4BI7B0DSWK40KV1IIRrn'
>>> child.interact()
iosv-1#show run | i hostname
hostname iosv-1
iosv-1#exit
Connection closed by foreign host.
>>>

You can get a lot of information about the child.spawn object by printing it out in string format:

>>> str(child)
"<pexpect.pty_spawn.spawn object at 0x7fb01e29dba8>ncommand: /usr/bin/telnetnargs: ['/usr/bin/telnet', '172.16.1.20']nsearcher: Nonenbuffer (last 100 chars): b''nbefore (last 100 chars): b'NTERPRISEK9-M), Version 15.6(2)T, RELEASE SOFTWARE (fc2)rnProcessor board ID 9MM4BI7B0DSWK40KV1IIRrn'nafter: b'iosv-1#'nmatch: <_sre.SRE_Match object; span=(164, 171), match=b'iosv-1#'>nmatch_index: 0nexitstatus: 1nflag_eof: Falsenpid: 2807nchild_fd: 5nclosed: Falsentimeout: 30ndelimiter: <class 'pexpect.exceptions.EOF'>nlogfile: Nonenlogfile_read: Nonenlogfile_send: Nonenmaxread: 2000nignorecase: Falsensearchwindowsize: Nonendelaybeforesend: 0.05ndelayafterclose: 0.1ndelayafterterminate: 0.1"
>>>

The most useful debug tool for Pexpect is to log the output in a file:

>>> child = pexpect.spawn('telnet 172.16.1.20')
>>> child.logfile = open('debug', 'wb')