Adding processed class attribute to mapping to get a Model's list of columns from class_mapper introspection

Question

How could I get the list of a Model's columns (and later of id columns, and relationships) as:

columns = Model.cols_list

so that the list would be constructed one time and reused when needed.

I would have writen something like this, that I can't get to work :

from sqlalchemy.orm import class_mapper

class Model(DeclarativeBase):
    __tablename__ = 'model_table'
    id = Column(Integer, primary_key=True, autoincrement=True)
    col1 = Column(...)
    col2 = Column(...)
    ...

    cols_list = None

    @classmethod
    def cols_list(cls):
        if cls.cols_list is None:
            cls.cols_list = [key.name for key in class_mapper(cls).primary_key]
        return cls.cols_list

Did you try Model.__table__.columns?

Alvaro Fuentes
– Alvaro Fuentes

2014-02-04 17:22:19 +00:00
Commented Feb 4, 2014 at 17:22 — Alvaro Fuentes
– Alvaro Fuentes, Commented Feb 4, 2014 at 17:22

zzzeek · Accepted Answer · 2014-02-10 05:35:53Z

1

class Model(DeclarativeBase):
    __tablename__ = 'model_table'
    id = Column(Integer, primary_key=True, autoincrement=True)
    col1 = Column(...)
    col2 = Column(...)

    @classmethod
    def col_list(cls):
        mapper = inspect(cls)
        return mapper.columns  

    @classmethod
    def relationships(cls):
        mapper = inspect(cls)
        return mapper.relationships

http://docs.sqlalchemy.org/en/rel_0_9/orm/mapper_config.html#sqlalchemy.orm.mapper.Mapper.columns

http://docs.sqlalchemy.org/en/rel_0_9/orm/mapper_config.html#sqlalchemy.orm.mapper.Mapper.column_attrs

http://docs.sqlalchemy.org/en/rel_0_9/orm/mapper_config.html#sqlalchemy.orm.mapper.Mapper.relationships

http://docs.sqlalchemy.org/en/rel_0_9/orm/mapper_config.html#sqlalchemy.orm.mapper.Mapper.attrs

etc.

answered Feb 10, 2014 at 5:35

zzzeek

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