simple command prompt example in Python - https://repl.it/IZGR/1

IZGR-1.py

import platform
import getpass
from os import getcwd, popen, chdir
import socket 

validos = ['windows', 'linux']
def cmd(*, os:str=None):
  running = True
  while running == True:
    if not cmd:
      continue
    
    if not os or os.lower() not in validos:
      os = platform.uname()[0].lower()
   
    if os.lower() == 'windows':
      path = getcwd()
      prefix = '{path}>'.format(path=path)
    elif os.lower() == 'linux':
      path = getcwd()
      user = getpass.getuser()
      system = socket.gethostname()
      prefix = '{user}@{system}:{path}$'.format(user=user, system=system, path=path)
    
    command = input(prefix)
    
    if command.startswith('cd ') and command.split('cd ')[1]:
      try:
        chdir(command.split('cd ')[1])
      except:
        print('Invalid Directory')
        continue
    if command != 'exit':
      print(popen(command).read())
    else:
      running = False

cmd()