问题描述
我正在使用 ibm_db2 驱动程序和 sqlalchemy 处理 IBM DB2 数据库.我的模型是:
I'm working with a IBM DB2 database using ibm_db2 driver and sqlalchemy. My model is:
class User(Model): id = Column('UID', Integer, primary_key=True) user = Column('USER', String(20)) password = Column('PASSWORD', String(10)) name = Column('NAME', String(30))
数据库中的字符串字段(例如 name)采用以下形式:
String fields from the database (e.g. name) comes in the form of:
>>> "John "
,其中值由模式填充到字段的完整长度.
, where the value is filled right with blanks to the full length of the field by schema.
我需要将此行为更改为在 query.all():
I need to change this behavior to the sqlalchemy type String (or a derivative thereof) produced follow (e.g. value.strip()) before output results by query.all():
>>> "John"
我该怎么做?
@property 装饰器不适用.我需要更改标准 sqlalchemy String 类的行为.
@property decorator is not applicable. I need to change the behavior of a standard sqlalchemy String class.
推荐答案
我不想改变标准 String 的行为,而是创建一个新类型(然后你可以将它重命名为 String per module based 或其他)但是这样最干净:
I would not want to change the behaviour of the standard String but to make a new type (you can then rename it to String per module basis or whatever) but it is cleanest that way:
from sqlalchemy import types class StrippedString(types.TypeDecorator): """ Returns CHAR values with spaces stripped """ impl = types.String def process_bind_param(self, value, dialect): "No-op" return value def process_result_value(self, value, dialect): """ Strip the trailing spaces on resulting values. If value is false, we return it as-is; it might be none for nullable columns """ return value.rstrip() if value else value def copy(self): "Make a copy of this type" return StrippedString(self.impl.length)
现在您可以使用 StrippedString 代替 String
Now you can use StrippedString instead of String