用户名和密码注册、登录系统，SQLite数据库版本

import hashlib
import pickle, os
import hmac, random
import sqlite3


def hmac_sha1(key, s):
 return hmac.new(key.encode('utf-8'), s.encode('utf-8'), 'MD5').hexdigest()


conn = sqlite3.connect('user.db')
cursor = conn.cursor()
try:
 cursor.execute('create table userpass (name varchar(20) primary key, password varchar(20))')
except Exception as e:
 pass

# 建立或者链接数据库
# conn = sqlite3.connect('user.db')
# cursor = conn.cursor()
# try:
# cursor.execute('create table userpass (name varchar(20), password varchar(20))')
# except Exception as e:
# print('Error: ', e)

# 获取用户名和密码信息
# if os.path.exists('/Users/lewisliu/user_information.txt'):
# with open('/Users/lewisliu/user_information.txt', 'rb') as f:
# user_information = pickle.load(f)
# else:
# user_information = dict()

# 注册或者登录
while True:
 # conn = sqlite3.connect('user.db')
 # cursor = conn.cursor()
 # try:
 # cursor.execute('create table userpass (name varchar(20) primary key, password varchar(20))')
 # except Exception as e:
 # pass
 # print('Error: ', e)

 # 选择模式，注册、登录、退出
 model = input("pleas input enroll/login/exit:")
 if model == 'enroll':
 name = input("please input your name:")
 # 用户名重复识别
 flag = cursor.execute("select name from userpass where name='%s'" % name).fetchone()
 if flag:
 print('name is exist!')
 else:
 password = input("please input your password:")
 key = 'liu' # ''.join([chr(random.randint(48, 122)) for i in range(20)])
 password = hmac_sha1(key, password)
 cursor.execute("insert into userpass (name, password) values ('%s','%s')" % (name, password))
 conn.commit()
 # conn.close()
 # if name in user_information.keys():
 # print("name is occupied!")
 # continue
 # password = input("please input your password:")
 # # 数据库添加用户名和密码
 # key = 'liu' # ''.join([chr(random.randint(48, 122)) for i in range(20)])
 # user_information[name] = hmac_sha1(key, password)
 # sha1 = hashlib.sha1()
 # sha1.update(password.encode('utf-8'))
 # user_information[name] = sha1.hexdigest()
 elif model == 'login':
 name = input("please input your name:")
 flag = cursor.execute("select name from userpass where name='%s'" % name).fetchone()
 if flag:
 password = input("please input your password:")
 key = 'liu'
 password = hmac_sha1(key, password)
 flag = cursor.execute("select name and password from userpass where name = '%s' and password='%s'" % (name, password)).fetchone()
 if flag:
 print("Wellcome!")
 else:
 print("wrong password! Exit!")
 conn.close()
 exit()
 else:
 print("name is not exist!")
 # if name not in user_information.keys():
 # # print("name is not exist!")
 # # continue
 # # password = input("please input your password:")
 # # key = 'liu' # ''.join([chr(random.randint(48, 122)) for i in range(20)])
 # # password = hmac_sha1(key, password)
 # # # sha1 = hashlib.sha1()
 # # # sha1.update(password.encode('utf-8'))
 # # # password = sha1.hexdigest()
 # # if user_information[name] == password:
 # # print("Wellcome!")
 # # else:
 # # print("wrong name or password! Exit!")
 # # with open('/Users/lewisliu/user_information.txt', 'wb') as f:
 # # pickle.dump(user_information, f)
 # # exit()
 elif model == 'exit':
 conn.close()
 exit()
 # with open('/Users/lewisliu/user_information.txt', 'wb') as f:
 # pickle.dump(user_information, f)
 # exit()
 else:
 print("model wrong!")