47 lines
1.6 KiB
Python
47 lines
1.6 KiB
Python
# -*- coding: utf-8 -*-
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"""
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Day_4 参考解答
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=============
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主题：面向对象（一）—— 类和实例。
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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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class User:
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all_users = [] # 类属性：模拟数据库表
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def __init__(self, name, email, age):
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self.name = name
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self.email = email
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self.age = age
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User.all_users.append(self) # 把新用户"存表"
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def get_full_name(self):
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return f"用户：{self.name}（{self.email}）"
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def __str__(self):
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# 给"人"看的：print(user) 时显示，Django admin 列表里显示的就是它
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return self.name
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def __repr__(self):
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# 给"开发者调试"看的：要能还原出原对象，eval(repr(u)) 应得到相同信息
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return f"User(name={self.name!r}, email={self.email!r}, age={self.age!r})"
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if __name__ == '__main__':
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u1 = User("zhangsan", "zs@163.com", 20)
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u2 = User("lisi", "ls@163.com", 21)
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u3 = User("wangwu", "ww@163.com", 19)
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for u in User.all_users:
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print(u, "->", repr(u))
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# zhangsan -> User(name='zhangsan', email='zs@163.com', age=20)
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# lisi -> User(name='lisi', email='ls@163.com', age=21)
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# wangwu -> User(name='wangwu', email='ww@163.com', age=19)
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restored = eval(repr(u1)) # __repr__ 的用途：可还原
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print(restored.name, restored.email) # zhangsan zs@163.com
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# 思考题答案：
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# __str__ 面向普通用户/展示，__repr__ 面向开发者/调试，且要求无歧义可还原；
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# 只实现 __repr__ 时，print() 会退而使用 __repr__；反之不会。
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