python拓展 - 技术栈

1.题目讲解

python经典题目--素数的判断

2.位运算

题目：计算56及-18的所有位运算符结果，并使在注释中体现计算过程

python 复制代码

a = 56
b = -18

# 56 二进制：00111000
# -18 补码：计算机负数用补码存储，18=00010010，取反11101101，+1 → 11101110

# 按位与 & ：两位都为1结果才是1
res_and = a & b
"""
00111000
11101110
--------
00101000 → 40
"""
# 按位或 |：任意一位为1则为1
res_or = a | b
"""
00111000
11101110
--------
11111110 → -2
"""

# 按位异或 ^：两位不同为1，相同为0
res_xor = a ^ b
"""
00111000
11101110
--------
11010110 → -42
"""

# 按位取反 ~：按位全部取反，公式 ~x = -x-1
res_tilde_a = ~a   # ~56 = -56‑1 = -57
res_tilde_b = ~b   # ~(-18) = 17

# 左移 << 二进制整体向左移动，低位补0
res_a_left = a << 1  # 56<<1  00111000 <<1 → 01110000 =112
res_b_left = b << 1  # -18 <<1 =‑36

# 右移 >> 整体右移，符号位填充
res_a_right = a >>1  #56>>1 → 00011100 =28
res_b_right = b >>1  #‑18 >>1 =‑9

print(f"56 & -18 = {res_and}")
print(f"56 | -18 = {res_or}")
print(f"56 ^ -18 = {res_xor}")
print(f"~56 = {res_tilde_a} , ~-18 = {res_tilde_b}")
print(f"56 <<1 = {res_a_left}, -18<<1 = {res_b_left}")
print(f"56 >>1 = {res_a_right}, -18>>1 = {res_b_right}")

3.完成文件读取功能

题目：任意读取某个文件内容时，请编写装饰器，实现写出文件时增加当前系统时间，并打印至控制台最后一行

python 复制代码

from datetime import datetime

# 装饰器：给写文件功能增加时间
def add_time_decorator(func):
    def wrapper(*args,**kwargs):
        # 执行原函数
        result = func(*args,**kwargs)
        now = datetime.now()
        time_str = str(now)
        # args[0] 文件名
        filename = args[0]
        # 追加写入时间到文件最后一行
        with open(filename,"a",encoding="utf‑8") as f:
            f.write(f"\n{time_str}")
        # 控制台打印时间
        print(f"【系统时间】{time_str}")
        return result
    return wrapper


# 读取文件函数
def read_file(filename):
    with open(filename,"r",encoding="utf‑8") as f:
        content = f.read()
    return content

# 被装饰的写文件函数
@add_time_decorator
def write_file(filename,content):
    with open(filename,"w",encoding="utf‑8") as f:
        f.write(content)


# 测试
# write_file("test.txt","测试文本内容")
# print(read_file("test.txt"))

4.给定一个包含n+1个整数的数组nums

题目： 给定一个包含n+1个整数的数组nums，其数字在1到n之间(包含1和n),可知至少存在一个重复的整数假设只有一个重复的整数，请找出这个重复的数

python 复制代码

def find_duplicate(nums):
    slow = nums[0]
    fast = nums[0]
    while True:
        slow = nums[slow]
        fast = nums[nums[fast]]
        if slow == fast:
            break
    # 找入口
    p1 = nums[0]
    p2 = slow
    while p1 != p2:
        p1 = nums[p1]
        p2 = nums[p2]
    return p1

#测试
print(find_duplicate([2,2,2,2,2]))

5.完成登录系统

题目：登录时数据使用序列化和反序列化

python 复制代码

import pickle

USER_FILE = "user.data"

# 注册：序列化保存用户账号密码
def register(username,password):
    user_data = {"username":username,"password":password}
    with open(USER_FILE,"wb") as f:
        pickle.dump(user_data,f) #序列化写入文件
    print("注册成功")

# 登录：反序列化读取文件，校验账号密码
def login(input_user,input_pwd):
    try:
        with open(USER_FILE,"rb") as f:
            user = pickle.load(f) #反序列化，读取数据
        if user["username"] == input_user and user["password"] == input_pwd:
            return True,"登录成功"
        else:
            return False,"账号或密码错误"
    except FileNotFoundError:
        return False,"无用户数据，请先注册"


# --------测试演示--------
# register("admin","123456")
# flag,msg = login("admin","123456")
# print(msg)
# flag,msg = login("admin","666")
# print(msg)