signup1.py

import os


def Signup():
    while True:
        uname = input('Username: ')
        fname = uname + '.dat'
        if ' ' in uname:
            print('SPACE in username, pls try again!')
            continue
        else:
            if os.path.exists(fname):
                print(f'username {uname} already exists, pls try again!')
                continue
            else:
                # Username OK
                break

    while True:
        password = input('Password: ')
        confirm_password = input('Confirm Password: ')
        if password == confirm_password:
            # password OK
            break
        else:
            print('Passwords do not match, pls try again')
            continue

    # Saving password in username.dat file
    file = open(fname, 'w')
    file.write(password)
    file.close()
    print('Signup Successfully...')


def Signin():
    while True:
        uname = input('Username: ')
        password = input('Password: ')
        fname = uname + '.dat'

        if os.path.exists(fname):
            # Username OK
            file = open(fname, 'r')
            password_in_file = file.read().rstrip()  # to remove Enter key \n
            file.close()
            if password == password_in_file:
                print('Signin Successfully....')
                # Main Code here
                break
            else:
                print('Wrong password...')
                ans = input('Exit or Continue? (e\\c)')
                if ans == 'e':
                    exit()
                else:
                    continue

        else:
            print(f'Username {uname} does not exists, pls try again')
            continue


# Program Start Here
# Signup()
Signin()