使用Sqlite3在python中创建登录和注册系统

Question

  

您好，我在编程方面还很陌生。我一直试图第一次使用sqlite3进行此登录和注册程序。如您所见，我编写check_username函数的方式不正确，因为在循环外部使用了Break。您能否以一种不会产生语法错误的方式帮助我重新排列代码。任何建议都将非常有帮助。

import re
import sqlite3


specialChar = ['$', '#', '@', '!', '*']
connection = sqlite3.connect("login_database.db")
cursor = connection.cursor()



def creat_table():
    cursor.execute("""CREATE TABLE IF NOT EXISTS Register
                   (username TEXT, password TEXT)""")
    connection.commit()

def insert_info(userN, passW):
    cursor.execute("INSERT INTO Register VALUES(?,?)", (userN, passW))
    connection.commit()

def check_username_taken(userN):
    while True:
        userN = input("create a username: ")
        cursor.execute("SELECT * FROM Register WHERE username=?", (userN,))
        fetch = cursor.fetchone()
        connection.commit()
        if fetch is not None:
            print("username taken")
        else:
            break

def check_username_exit(userN):
    cursor.execute("SELECT * FROM Register WHERE username=?", (userN,))
    fetch = cursor.fetchone()
    connection.commit()
    if fetch is not None:
        break
    else:
        print("username is not registered.")


print("1.Register \n2.Login \n3.exit")
while True:
    decision = input("What would you like to do? ")
    if decision == "1":
        while True:
            userN = input("create a username: ")
            check_username_taken()
        while True:
            passW = input("creat a password: ")
            if len(passW) < 6:
                print("Your password should at least contain 6 charcters.")
            elif re.search("[0-9]", passW) is None:
                print("Your password must contain at least one number.")
            elif re.search("[a-z]", passW) is None:
                print("Your password must contain at least one letter.")
            elif not any(c in specialChar for c in passW):
                print("Your password must contain at least one spcial character.")
            else:enter code here
                insert_info()
                print("Password is set!")
                break

    if decision == "2":
        while True:
            userN = input("Username: ")
            check_username_exit()
        x = 0
        while x !=1 :
            passW = input("Password: ")
            for key,val in list.items():
                if key == userN and val == passW:
                    print("logging in ...")
                    x = 1
                    break
                else:
                    print("wrong combination.")
                    break


    if decision == "3":
        print("\nEnd of the program!")
        exit()