
(推荐操作系统:windows7系统、Python 3.9.1、DELL G3电脑。)
1、定义Field类,它负责保存数据库表的字段名和字段的类型:
1 2 3 4 | class Field(object):
def __init__(self, name, column_type):
self.name = name
self.column_type = column_type
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2、在Field的基础上,进一步定义各种具体类型的Field,比如StringField,IntegerField等等:
1 2 3 4 5 6 7 | class StringField(Field):
def __init__(self, name, max_length):
super (StringField, self).__init__(name, 'varchar(%d)' % max_length)
class IntegerField(Field):
def __init__(self, name):
super (IntegerField, self).__init__(name, 'int' )
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3、下一步,就是编写最复杂的ModelMetaclass了:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | class ModelMetaclass(type):
def __new__(cls, name, bases, attrs):
if name == 'Model' :
return type.__new__(cls, name, bases, attrs)
print( 'Found model: %s' % name)
mappings = dict()
for k, v in attrs.items():
if isinstance(v, Field):
mappings[k] = v
for k in mappings.keys():
attrs.pop(k)
attrs[ '__mappings__' ] = mappings
attrs[ '__table__' ] = name
return type.__new__(cls, name, bases, attrs)
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4、创建User类,并调用save方法,保存:
1 2 3 4 5 6 7 8 9 10 | class User(Model):
id = IntegerField( 'id' )
name = StringField( 'username' , max_length=48)
email = StringField( 'email' , max_length=128)
password = StringField( 'password' , max_length=24)
# 创建一个实例:
u = User(id=12345, name= 'xiaoming' , email= 'xiaoming@xiaomi.com' , password= 'test' )
# 保存到数据库:
u.save()
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以上就是python简单实现了一个ORM,希望能对大家有所帮助。更多Python学习指路:python基础教程