一、统计文件中所有字符及其出现次数（不区分大小写）

任务要求统计一个文本文件中每个字符的出现次数，忽略大小写，并将标点符号和空格也包含在内。

# 统计文件中的字符频率
from collections import defaultdict

result_dict = defaultdict(int)

with open('data.txt', 'r', encoding='utf-8') as file:
    content = file.read().lower()
    for char in content:
        result_dict[char] += 1

print(dict(result_dict))

二、统计文件中大写字母、小写字母、数字及其他字符的数量

此任务需要对文件内容进行分类统计，包括大写字母、小写字母、数字和其他字符。

stats = {'大写字母': 0, '小写字母': 0, '数字': 0, '其他字符': 0}

with open('data2.txt', 'r', encoding='utf-8') as file:
    content = file.read()
    for char in content:
        if char.isupper():
            stats['大写字母'] += 1
        elif char.islower():
            stats['小写字母'] += 1
        elif char.isdigit():
            stats['数字'] += 1
        else:
            stats['其他字符'] += 1

print(stats)

三、用户登录注册系统

设计一个简单的用户管理系统，支持用户注册、登录功能，并具备错误处理和数据持久化能力。

import time

USER_DB = 'users.txt'
BLACKLIST_DB = 'blacklist.txt'

def load_users():
    users = {}
    with open(USER_DB, 'r', encoding='utf-8') as f:
        for line in f:
            username, password, remark = line.strip().split('|')
            users[username] = {'password': password, 'remark': remark}
    return users

def save_user(username, password, remark):
    with open(USER_DB, 'a', encoding='utf-8') as f:
        f.write(f"{username}|{password}|{remark}\n")

def blacklist_user(username):
    with open(BLACKLIST_DB, 'a', encoding='utf-8') as f:
        f.write(f"{username}\n")

def is_blacklisted(username):
    with open(BLACKLIST_DB, 'r', encoding='utf-8') as f:
        return username in [line.strip() for line in f]

def register():
    while True:
        username = input("请输入用户名：")
        password = input("请输入密码：")
        confirm_password = input("请再次输入密码：")
        remark = input("请输入备注信息（可选）：") or "无"
        
        if password != confirm_password:
            print("两次输入的密码不一致，请重新尝试！")
            continue
        
        users = load_users()
        if username in users:
            print("该用户名已存在，请选择其他用户名！")
        else:
            save_user(username, password, remark)
            print("注册成功！")
            break

def login():
    attempts = 0
    max_attempts = 3
    
    while attempts < max_attempts:
        username = input("请输入用户名：")
        password = input("请输入密码：")
        
        if is_blacklisted(username):
            print("该用户已被锁定，请联系管理员！")
            return
        
        users = load_users()
        if username in users and users[username]['password'] == password:
            print("登录成功！")
            return
        else:
            attempts += 1
            print(f"用户名或密码错误，您还有 {max_attempts - attempts} 次机会！")
    
    if attempts >= max_attempts:
        print("多次登录失败，账户已被锁定！")
        blacklist_user(username)

def main():
    while True:
        print("\n1. 注册\n2. 登录\n0. 退出")
        choice = input("请选择操作：")
        
        if choice == '1':
            register()
        elif choice == '2':
            login()
        elif choice == '0':
            print("感谢使用，再见！")
            break
        else:
            print("无效选项，请重试！")

if __name__ == '__main__':
    main()