[英]When the sqlalchemy ORM class attributes are different from database columns, how to get a list of the ORM class attributes?
假設您要遍歷sqlalchemy中ORM類的ORM屬性。 因此,您需要ORM屬性的列表。 您如何獲得該清單?
如果ORM類未重命名屬性,因此ORM屬性與數據庫列匹配,則可以使用以下解決方案: https : //stackoverflow.com/a/24748320/1023033 (順便說一句,還有一個內置的源代碼文件/lib/sqlalchemy/orm/base.py中的(私有)函數_orm_columns()似乎提供了此功能)
但是,如果python ORM類的名稱與數據庫列的名稱不同(例如,在這3個ORM屬性中):
>>> class User(Base):
... __tablename__ = 'users'
...
... id = Column('pkey', Integer, primary_key=True)
... name = Column('user_name', String)
... fullname = Column('human_name', String)
那么該方法不起作用。 那么,如何獲得ORM屬性的python版本?
這已經使用檢查系統實現 :
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import inspect
Base = declarative_base()
class A(Base):
__tablename__ = 'a'
id = Column(Integer, primary_key=True)
x = Column(Integer)
y = Column(Integer)
print inspect(A).c
print inspect(A).c.x
print inspect(A).column_attrs
print inspect(A).column_attrs.x
print inspect(A).column_attrs.x.expression
http://docs.sqlalchemy.org/en/latest/core/inspection.html
http://docs.sqlalchemy.org/en/latest/orm/mapping_api.html#sqlalchemy.orm.mapper.Mapper.columns
http://docs.sqlalchemy.org/en/latest/orm/mapping_api.html#sqlalchemy.orm.mapper.Mapper.column_attrs
http://docs.sqlalchemy.org/en/latest/orm/mapping_api.html#sqlalchemy.orm.mapper.Mapper.c
我定義了一個mixin類來增強
Base = declarative_base()
mixin類的定義為:
import inspect
import sqlalchemy as sqla
class orm_mixin_class(object):
"""Additional functionality wanted in orm classes (that inherit from Base)."""
@classmethod
def orm_class_info(cls):
"""
Get info about the orm class (as opposed to the database table it is mapped to).
Returns:
list of dict where each dict describes a orm class attribute.
Keys: s_class_attribute_name
"""
o_leaf_level_class = cls # this turns out the be the leaf class instead of this mixin class
l_orm_attribute_pairs = inspect.getmembers(o_leaf_level_class)
l_orm_class_info_dicts = []
for (s_class_attribute_name, o_attr_type) in l_orm_attribute_pairs:
d_attr_info = {}
b_orm_attribute = False
try:
o_inspect = sqla.inspection.inspect(o_attr_type)
if isinstance(o_inspect, sqla.orm.attributes.QueryableAttribute):
b_orm_attribute = True
d_attr_info['s_class_attribute_name'] = s_class_attribute_name
except:
pass
if b_orm_attribute:
# only orm attributes have an entry in the output list
l_orm_class_info_dicts.append(d_attr_info)
return(l_orm_class_info_dicts)
因此,可以從方法調用中輕松獲得ORM屬性列表。
現在,ORM類聲明為:
class User(Base, orm_mixin_class):
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