python 简单的ORM蟒蛇

Posted 2021-05-09

#coding:utf-8
class Field(object):
    def __init__(self,column_type, max_length, **kwargs):
        self.column_type = column_type
        self.max_length = max_length
        self.default = None
        if kwargs:
            for k,v in kwargs.items():
                if hasattr(self,k):
                    setattr(self,k,v)

    def __str__(self):
        return '<%s>'%(self.__class__.__name__)

'''
Field Type
'''
class StringField(Field):
    def __init__(self, max_length=30, **kwargs):
        # column_type：类型varchar，max_length：长度
        super(StringField,self).__init__(column_type='varchar({})'.format(max_length),max_length=max_length,**kwargs)


class IntegerField(Field):
    def __init__(self, **kwargs):
        super(IntegerField,self).__init__(column_type='bigint', max_length=11)


class ModelMetaclass(type):
    def __new__(cls, name, bases, attrs):
        if name == 'Model':
            return type.__new__(cls, name,bases,attrs)

        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__'] = attrs.get('Meta').table or name
        return type.__new__(cls, name, bases, attrs)

from functools import reduce
class Model(dict):
    __metaclass__ = ModelMetaclass
    def __init__(self,**kw):
        super(Model, self).__init__(**kw)

    def __getattr__(self, item):
        try:
            return self[item]
        except:
            raise AttributeError(r"'Model' 对象没有%s属性"%item)

    def __setattr__(self, key, value):
        self[key] = value


    def save(self):
        '''
        insert data in MySQL Table
        :return: SQL about insert data
        '''
        fields = []
        params = []
        for k,v in self.__mappings__.items():
            fields.append(k)
            params.append(getattr(self,k,v.default))
        sql = 'insert into {} ({}) values ({})'.format(self.__table__, self.join(fields), self.join(params))

        print('SQL:%s'%sql)

        return sql

    def join(self, attrs, pattern=','):
        return reduce(lambda x,y:'{}{}{}'.format(x,pattern,y),attrs)

'''
Test Model
'''

class User(Model):
    class Meta:
        table='users'
    id = IntegerField()
    name = StringField()
    email = StringField(max_length=50, default='[e-mail]')
    password = StringField(max_length=50)

if __name__ == '__main__':
    u = User(id=12345, name='ayuliao', email='[e-mail]', password='my-pwd')
    u.save()