161 lines
5.3 KiB
Python
161 lines
5.3 KiB
Python
# -*- coding: utf-8 -*-
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"""
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Day_2 参考解答
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=============
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今天的题目只用基础语法，但每个都是后端开发的真实场景。
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建议：先自己写，写不出来再看；看完后把代码关掉，自己再默写一遍。
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"""
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import time
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# ============================================================
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# 题目一：解析 URL 查询参数
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# ============================================================
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def parse_query_string(query):
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"""把 'username=zhangsan&age=20' 解析成 {'username': 'zhangsan', 'age': '20'}"""
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result = {}
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if not query: # 边界 1：空输入
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return result
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for item in query.split('&'): # 先按 & 切成若干段
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if '=' in item:
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key, value = item.split('=', 1) # maxsplit=1：值里可能也含有 '='，只切第一个
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else:
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key, value = item, '' # 边界 3：没有 = 的参数，值记为空字符串
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result[key] = value # 字典赋值天然处理"重复键覆盖"和"值为空"
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return result
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# 进阶：URL 编码还原（把 + 和 %20 还原成空格）
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def url_decode(value):
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return value.replace('+', ' ').replace('%20', ' ')
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def parse_query_string_advanced(query):
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result = {}
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if not query:
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return result
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for item in query.split('&'):
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if '=' in item:
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key, value = item.split('=', 1)
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else:
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key, value = item, ''
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result[key] = url_decode(value)
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return result
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# 一个小测试
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if __name__ == '__main__':
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print(parse_query_string('username=zhangsan&age=20&city=qingdao'))
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# {'username': 'zhangsan', 'age': '20', 'city': 'qingdao'}
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print(parse_query_string('name=a&name=b&flag'))
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# {'name': 'b', 'flag': ''}
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print(parse_query_string(''))
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# {}
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print(parse_query_string_advanced('name=Zhang+San&city=A%20B'))
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# {'name': 'Zhang San', 'city': 'A B'}
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# ============================================================
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# 题目二：万能日志记录器
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# ============================================================
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def log_call(func, label=""):
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"""给函数包一层日志。func 被调用时打印参数和耗时。"""
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def wrapper(*args, **kwargs):
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tag = f"[{label}] " if label else ""
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print(f"{tag}[LOG] 调用函数 {func.__name__}，参数为 args={args}, kwargs={kwargs}")
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start = time.time()
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result = func(*args, **kwargs) # 原样透传参数
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elapsed = time.time() - start
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print(f"{tag}[LOG] {func.__name__} 执行完成，耗时 {elapsed:.4f} 秒")
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return result # 原样返回结果
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return wrapper
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@log_call # 等价于 add = log_call(add)
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def add(a, b):
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return a + b
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def multiply(a, b):
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return a * b
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multiply = log_call(multiply, label="核心计算") # 进阶：带标签
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if __name__ == '__main__':
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print(add(1, 2))
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print(multiply(3, 4))
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# 输出示例：
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# [LOG] 调用函数 add，参数为 args=(1, 2), kwargs={}
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# [LOG] add 执行完成，耗时 0.0000 秒
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# 3
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# [核心计算][LOG] 调用函数 multiply，参数为 args=(3, 4), kwargs={}
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# [核心计算][LOG] multiply 执行完成，耗时 0.0000 秒
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# 12
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# ============================================================
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# 题目三：模拟注册接口的参数校验
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# ============================================================
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class ValidationError(Exception):
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"""自定义校验异常：参数不合法时抛出"""
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pass
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def validate_registration(data):
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username = data.get("username")
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email = data.get("email")
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age = data.get("age")
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if not username or len(username) < 3:
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raise ValidationError("用户名必须存在且长度不少于 3")
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if not email or "@" not in email or "." not in email:
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raise ValidationError("邮箱必须包含 @ 和 .")
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if age is None:
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raise ValidationError("年龄必须存在")
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try:
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age_int = int(age) # 字符串 "20" 也能转
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except (TypeError, ValueError):
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raise ValidationError("年龄必须是整数")
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if not (1 <= age_int <= 120):
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raise ValidationError("年龄必须在 1~120 之间")
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def register():
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data = {"username": "zhangsan", "email": "zs@163.com", "age": "20"}
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try:
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validate_registration(data)
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print(f"注册成功，欢迎 {data['username']}！")
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except ValidationError as e:
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print(f"校验失败: {e}")
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# ---- 进阶：把规则做成数据 ----
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def is_valid_email(email):
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return isinstance(email, str) and "@" in email and "." in email
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def validate(data, rules):
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"""rules: {字段名: (校验函数, 错误信息)}，返回所有错误列表"""
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errors = []
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for field, (check, message) in rules.items():
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if not check(data.get(field)):
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errors.append(f"{field}: {message}")
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return errors
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RULES = {
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"username": (lambda v: isinstance(v, str) and len(v) >= 3, "用户名长度不足 3"),
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"email": (is_valid_email, "邮箱格式不正确"),
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"age": (lambda v: isinstance(v, int) and 1 <= v <= 120, "年龄非法"),
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}
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if __name__ == '__main__':
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register() # 注册成功，欢迎 zhangsan！
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print(validate({"username": "zs", "email": "bad", "age": 200}, RULES))
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# ['username: 用户名长度不足 3', 'email: 邮箱格式不正确', 'age: 年龄非法']
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