TypeError using Telnet.write()

Question

I have the following code:

try:
    tn = Telnet(host, str(port))
except Exception as e:
    print("Connection cannot be established", e)
    traceback.print_exc()
print("You are connected")
tn.write('command?'+'\r\n')
while True:
    line = tn.read_until("\n")

When I run this code on machine X everything is working just fine, but when when I try to run the same code on a different machine I end up with the following error:

 Traceback (most recent call last):
 File
 "C:/Users/admin/Documents/Projects/terminalManager/terminalManager.py", line 50, in <module>
 terminalManager()
 File
"C:/Users/admin/Documents/Projects/terminalManager/terminalManager.py", line 16, in __init__
self.connect(terminalBganIp, terminalBganPort)
File "C:/Users/admin/Documents/Projects/terminalManager/terminalManager.py", line 34, in connect
tn.write('AT_IGPS?'+'\r\n')
File "C:\Program Files (x86)\Python\Python3.6.1\lib\telnetlib.py", line 287, in write
if IAC in buffer:
TypeError: 'in <string>' requires string as left operand, not bytes

Am I doing something wrong or is the second machine messing with me?

EDIT:

When i used IDLE debugger on my second machine everything is working. it seems it is not working when running it normally, is there anything i can do to resolve this?

Answer 1

I can't believe that the same code is working for you on another machine with the same python version.

Your issue is exactly what the Exception says it is TypeError: 'in <string>' requires string as left operand, not bytes. You need to provide bytes to tn.write instead of a string.

You can convert your string into bytes via encode:

command = "command?" + "\r\n"
tn.write(command.encode("ascii"))

Edit: Well, someone beat me to it :D

Answer 2

Try to do:

tn.write(('command?'+'\r\n').encode())

Usually sockets work over bytes not strings, the error could be related to that, hope this can help.