pip install pytn3270

from tn3270 import Telnet, Emulator, AID, CharacterCell

telnet = Telnet('IBM-3279-2-E')

telnet.open('mainframe', 23)

emulator = Emulator(telnet, 24, 80)

# Wait until the keyboard is unlocked.
while emulator.keyboard_locked:
    print('Waiting for keyboard to be unlocked...')

    emulator.update(timeout=1)

# Convert the screen contents to a string, replacing attribute cells with '@'.
#
# Note that this is not supposed to demonstrate an efficient implementation.
screen = ''

for cell in emulator.cells:
    if isinstance(cell, CharacterCell):
        byte = cell.byte

        if byte == 0:
            screen += ' '
        else:
            screen += bytes([byte]).decode('ibm037')
    else:
        screen += '@'

# Display the screen.
for line in [screen[index:index+80] for index in range(0, len(screen), 80)]:
    print(line)