15年底的时候写过一段时间Python，没有坚持下去，如今工作了，在业余生活中抽出时间重拾曾学习过的Python。
Python2.7
这是廖雪峰Python教程中的一段示例代码
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‘simple ORM using metaclass’
author = ‘summer’
class Field(object):
“"”docstring for Field”””
def init(self, name, column_type):
self.name = name
self.column_type = column_type
def str(self):
return ‘<%s:%s>’ % (self.class.name,self.name)
class StringField(Field):
“"”docstring for StringField”””
def init(self, name):
super(StringField,self).init(name,’varchar(100)’)
class IntegerField(Field):
“"”docstring for IntegerField”””
def init(self, name):
super(IntegerField, self).init(name,’bigint’)
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.iteritems():
if isinstance(v,Field):
print ('Found mapping: %s ==> %s' %(k,v) )
mappings[k] = v
for k in mappings.iterkeys():
attrs.pop(k)
attrs['__mappings__']=mappings # 保存属性和列的映射关系
attrs['__table__'] = name #假设表名和类名一致
return type.__new__(cls, name, bases, attrs) class Model(dict):
"""docstring for Model"""
__metaclass__ = ModelMetaClass
def __init__(self, **kw):
super(Model, self).__init__(**kw)
def __getattr__(self,key):
try:
return self[key]
except KeyError:
raise AttributeError(r"'Model' object has no attribute '%s'" % key)
def __setattr__(self,key,value):
self[key] = value
def save(self):
fields = []
params = []
args = []
for k ,v in self.__mappings__.iteritems():
fields.append(v.name)
params.append('?')
args.append(getattr(self,k,None))
sql = 'insert into %s (%s) values (%s)' % (self.__table__, ','.join(fields), ','.join(params))
print ('SQL: %s' % sql )
print ('ARGS: %s' % str(args))
testing code
class User(Model):
id = IntegerField('uid')
name = StringField('username')
email = StringField('email')
password = StringField('password')
u = User(id=12345,name=’summer’,email=’[email protected]’,password=’mypsd’)
u.save()
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