87 lines
2.9 KiB
Python
87 lines
2.9 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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主题：字典与字符串。
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建议：先自己写，写不出来再看；看完后关掉文件自己默写一遍。
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"""
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# ============================================================
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# 题目一：模拟查询结果的处理（热身）
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# ============================================================
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users = [
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{"name": "zhangsan", "age": 20, "city": "青岛"},
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{"name": "lisi", "age": 17, "city": "济南"},
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{"name": "wangwu", "age": 22, "city": "北京"},
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]
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# 1. 筛选年龄 ≥ 18
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adults = [u for u in users if u["age"] >= 18]
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# 2. 按年龄从大到小排序（key 指定按哪个字段排，reverse=True 表示降序）
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adults_sorted = sorted(adults, key=lambda u: u["age"], reverse=True)
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# 3. 格式化成字符串列表
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formatted = [f"{u['name']}({u['age']}岁)" for u in adults_sorted]
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# 4. 进阶：拼成一个字符串
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joined = ", ".join(formatted)
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if __name__ == '__main__':
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print(adults)
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print([u["name"] for u in adults_sorted])
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print(formatted)
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print(joined)
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# [{'name': 'zhangsan', 'age': 20, 'city': '青岛'}, {'name': 'wangwu', 'age': 22, 'city': '北京'}]
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# ['wangwu', 'zhangsan']
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# ['wangwu(22岁)', 'zhangsan(20岁)']
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# wangwu(22岁), zhangsan(20岁)
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# ============================================================
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# 题目二：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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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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