import getpass
userdb = {}
def register():
username = input('username: ')
if username in userdb:
print('%s already exists.' % username)
else:
password = input('password: ')
userdb[username] = password
def login():
username = input('username: ')
password = getpass.getpass("password: ")
if userdb.get(username) != password:
print('login failed')
else:
print('login successful')
def show_menu():
cmds = {'0': register, '1': login}
prompt = """(0) register
(1) login
(2) exit
Please input your choice(0/1/2): """
while True:
choice = input(prompt).strip()[0]
if choice not in '012':
print('Invalid inupt. Try again.')
continue
if choice == '2':
break
cmds[choice]()
if __name__ == '__main__':
show_menu()