python3: can't restore the out on console to a file from the program beginning to end& pexpect.EOF issue - python-3.x

Question

Below is my code about using pexpect module achieve SSH logon function.
#!/usr/bin/env python
import pexpect
import sys
#use ssh to logon server
user="inteuser" #username
host="146.11.85.xxx" #host ip
password="xxxx" #password
command="ls -l" #list file on home/user directory
child = pexpect.spawn('ssh -l %s %s %s'%(user, host, command))
child.expect('password:')
child.sendline(password)
childlog = open('prompt.log',"ab") # restore prompt log to file prompt.log
__console__ = sys.stdout # make a backup of system output to console
sys.stdout = childlog # print the system output to childlog
child.expect(pexpect.EOF)
childlog.close()
sys.stdout = __console__ # back to the original state of system output
print(child.before) # print the contents before match expect function
after I execute my script
[~/Liaohaifeng]$ python3 ssh_test.py
b' \r\ntotal 69636\r\n-rw-rw-r-- 1 inteuser inteuser 949 Nov 28 02:01
01_eITK_trtest01_CrNwid.log\r\n
[~/Liaohaifeng]$ cat prompt.log
total 69412
-rw-rw-r-- 1 inteuser inteuser 949 Nov 28 02:01 01_eITK_trtest01_CrNwid.log
I think this result is not my expected. when I remove the code child.expect(pexpect.EOF) in my script, the output about print(child.before) can be correct(it should print the content before matching password)
Below is the output after I remove child.expect(pexpect.EOF)
[~/Liaohaifeng]$ python3 ssh_test.py
b"\r\n-------------------------------------------------------------------------------\r\n...
These computer resources are provided for authorized users only. For legal,
\r\n
security and cost reasons, utilization and access of resources are sxx, in\r\n
accordance with approved internal procedures, at any time if IF YOU ARE NOT AN AUTHORIZED USER; PLEASE EXIT IMMEDIATELY...\r\n "
my purpose is print out all the output to a file after executing the script,but the log file still only contains the output of listing directory. So why this happen? could you please help update my script? thank you very much.

Answer 1

You can use the spawn().logfile_read.
[STEP 101] # cat example.py
import pexpect, sys
child = pexpect.spawn('bash --norc')
if sys.version_info[0] <= 2:
# python2
child.logfile_read = open('/tmp/pexpect.log', 'w')
else:
# python3
fp = open('/tmp/pexpect.log', 'w')
child.logfile_read = fp.buffer
child.expect('bash-[.0-9]+[$#] ')
child.sendline('echo hello world')
child.expect('bash-[.0-9]+[$#] ')
child.sendline('exit')
child.expect(pexpect.EOF)
child.logfile_read.close()
[STEP 102] # python3 example.py
[STEP 103] # cat /tmp/pexpect.log
bash-4.4# echo hello world
hello world
bash-4.4# exit
exit
[STEP 104] #

Answer 2

It is a simple question, just adjust code order is OK.
#!/usr/bin/env python
import pexpect
import sys
#use ssh to logon server
user="inteuser" #username
host="146.11.85.xxx" #host ip
password="xxxx" #password
command="ls -l" #list file on home/user directory
child = pexpect.spawn('ssh -l %s %s %s'%(user, host, command))
childlog = open('prompt.log',"ab")
child.logfile = childlog
child.expect('password:')
child.sendline(password)
child.expect(pexpect.EOF)
childlog.close()