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  1. # your code goes here
  2. class Field(object):
  3.  
  4.     def __init__(self, name, column_type):
  5.         self.name = name
  6.         self.column_type = column_type
  7.  
  8.     def __str__(self):
  9.         return '<%s:%s>' % (self.__class__.__name__, self.name)
  10.  
  11. class StringField(Field):
  12.     def __init__(self, name):
  13.         super(StringField, self).__init__(name, 'varchar(100)')
  14.  
  15. class IntegerField(Field):
  16.     def __init__(self, name):
  17.         super(IntegerField, self).__init__(name, 'bigint')
  18.  
  19. class ModelMetaclass(type):
  20.     def __new__(cls, name, bases, attrs):
  21.         if name=='Model':
  22.             return type.__new__(cls, name, bases, attrs)
  23.         print('Found model: %s' % name)
  24.         mappings = dict()
  25.         for k, v in attrs.items():
  26.             if isinstance(v, Field):
  27.                 print('Found mapping: %s ==> %s' % (k, v))
  28.                 mappings[k] = v
  29.         for k in mappings.keys():
  30.             attrs.pop(k)
  31.         attrs['__mappings__'] = mappings # 保存属性和列的映射关系
  32.         attrs['__table__'] = name # 假设表名和类名一致
  33.         return type.__new__(cls, name, bases, attrs)
  34.  
  35. class Model(dict, metaclass=ModelMetaclass):
  36.     def __init__(self, **kw):
  37.         super(Model, self).__init__(**kw)
  38.  
  39.     def __getattr__(self, key):
  40.         try:
  41.             temp=self[key]
  42.             print('quoted')
  43.             return temp
  44.         except KeyError:
  45.             raise AttributeError(r"'Model' object has no attribute '%s'" % key)
  46.  
  47.     def __setattr__(self, key, value):
  48.         self[key] = value
  49.  
  50.     def save(self):
  51.         fields = []
  52.         params = []
  53.         args = []
  54.         for k, v in self.__mappings__.items():
  55.             fields.append(v.name)
  56.             params.append('?')
  57.             args.append(getattr(self, k, None))
  58.         sql = 'insert into %s (%s) values (%s)' % (self.__table__, ','.join(fields), ','.join(params))
  59.         print('SQL: %s' % sql)
  60.         print('ARGS: %s' % str(args))
  61. class User(Model):
  62.     # 定义类的属性到列的映射：
  63.     id = IntegerField('id')
  64.     name = StringField('username')
  65.     email = StringField('email')
  66.     password = StringField('password')
  67.  
  68. # 创建一个实例：
  69. u = User(id=12345, name='Michael', email='test@orm.org', password='my-pwd')
  70. # 保存到数据库：
  71. u.save()
Success #stdin #stdout 0.04s 9584KB
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Standard input is empty
stdout
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Found model: User
Found mapping: id ==> <IntegerField:id>
Found mapping: name ==> <StringField:username>
Found mapping: email ==> <StringField:email>
Found mapping: password ==> <StringField:password>
quoted
quoted
quoted
quoted
SQL: insert into User (id,username,email,password) values (?,?,?,?)
ARGS: [12345, 'Michael', 'test@orm.org', 'my-pwd']
https://ideone.com/taw9bd
language:
Python 3 (python  3.9.5)
created:
8 days ago
visibility:
public

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