homework about a simple shell

new_shell.py

#!/usr/bin/env python2.7
# -*- coding:utf-8 -*-


import subprocess
import curses
import sys
import os


def init_once():
    """
    Init while starting
    """
    curses.setupterm()
    sys.stdout.write(curses.tigetstr("clear"))
    sys.stdout.flush()


def init_command():
    """
    Init while inputting
    """
    subprocess.call(['pwd'])
    commands = raw_input(">>>")
    return commands


def get_simcom(command):
    command_splited = command.split(" ")
    return command_splited


def run_command(command_list):
    if command_list[0] == 'cd':
        command = ' '.join(command_list[1:])
        os.chdir(command)
        return 0
    else:
        status = subprocess.call(command_list)
        return status


def main():
    init_once()

    while True:
        try:
            commands = init_command()
            command_splited = get_simcom(commands)
            try:
                status = run_command(command_splited)
                if status == 0:
                    pass
                elif status == 2:
                    print "arguments error,please check your arguments!"
            except OSError:
                print sys.exc_value[1]
                print "please check your command"
        except KeyboardInterrupt:
            print "\n"
            pass
        except EOFError:
            print "\n"
            ex = raw_input("Do you really want to exit ([Y]/N)?")
            if ex == "Y" or ex == "y" or ex == "":
                print "Bye~ >3<"
                break
            elif ex == "N" or ex == "n":
                pass
            else:
                print repr(ex)
                print "incorrect input!"


if __name__ == "__main__":
    main()