SQLAlchemy列结果处理 [英] SQLAlchemy Columns result processing
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 >)的形式为:
String fields from the database (e.g. name) comes in the form of:
>>> "John "
,其中值通过模式右边的空格完全填充为空白
, 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生成的sqlalchemy类型的String(或其派生类型),例如( value.strip())。在 query.all()输出结果之前:
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"
我该怎么办?
@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
我不想更改标准String的行为但是要创建一个新类型(您可以随后将其重命名为每个模块一个String或其他形式),但这是最干净的方法:
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
而不是 String
Now you can use StrippedString
instead of String
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