channel.recv_exit_status in paramiko always returns the return code of the first command executed over invoke_shell

[Samir]

I am getting some discrepancy in the return code below. May be I am not using in the proper way. Every-time I print the return code, it prints the same as the first one has returned. Do I need to reset the return code. I mean in the following example, I am getting the return code as 2 for both the commands. Now when I interchange both the commands, I mean replace ls -al;exit\n with ls -al file_not_exist;exit\n and vice versa, it prints return code 0. Each time it prints the same return code as the first one has returned.

ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect('localhost', username='sam', password='mypassword')

channel = ssh.invoke_shell()
channel.send('ls -al file_not_exist;exit\n') #Sending to list a file which doesn't exist
time.sleep(3)
print "My 1st command exit status is: ",channel.exit_status_ready()
print "My 1st command return code is: ", channel.recv_exit_status()

channel.send('ls -al;exit\n')
time.sleep(3)
print "My 2nd command exit status is: ",channel.exit_status_ready()
print "My 2nd command return code is: ",channel.recv_exit_status()

This should print the return code of each command. Please let me know if I am doing wrong somewhere.