Never mind. This problem is solved by join operations. Thanks for your attention. On Friday, January 28, 2022 at 4:16:05 AM UTC+13 Simon King wrote:
> I'm sorry, I still don't understand - what do you expect > query(Genome.attributes) to do? Can you give an example? > > Thanks, > > Simon > > On Wed, Jan 26, 2022 at 11:30 PM Simon <htlb...@gmail.com> wrote: > > > > Sorry for that the question is not clear. The question is how can we > query a database's property. > > > > Given the above example, if query(Genome.id) or > query(Genome.created_date), it works fine. But if I query the property, > query(Genome.attributes): it raises the exception. > > > > Thanks. > > Simon > > > > On Wednesday, January 26, 2022 at 12:53:52 AM UTC+13 Simon King wrote: > >> > >> Can you show the part of *your* code that is triggering the error, and > >> explain what you are trying to do? Plain python properties aren't > >> normally very useful when accessed via a class. "Genome.attributes" > >> returns a property object, not the return value from the function, and > >> I don't understand what you are trying to do with it. > >> > >> Thanks, > >> > >> Simon > >> > >> On Mon, Jan 24, 2022 at 2:03 AM Simon <htlb...@gmail.com> wrote: > >> > > >> > Hi there, > >> > > >> > I got a problem about 'sqlalchemy.exc.ArgumentError: SQL expression > object expected, got object of type <class 'property'> instead' > >> > > >> > My SQLAlchemy version is 1.3.22. I have a database like > >> > > >> > Class Genome: > >> > id = Column(Integer, primary_key=True) > >> > created_date = Column(Datetime, nullable=False) > >> > > >> > @property > >> > def attributes(self): > >> > return "something" > >> > > >> > > >> > If using the query, it reports an error through the elements.py in > the sqlAlchemy > >> > > >> > def _literal_as(element, text_fallback): > >> > if isinstance(element, Visitable): > >> > return element > >> > elif hasattr(element, "__clause_element__"): > >> > return element.__clause_element__() > >> > elif isinstance(element, util.string_types): > >> > return text_fallback(element) > >> > elif isinstance(element, (util.NoneType, bool)): > >> > return _const_expr(element) > >> > else: > >> > raise exc.ArgumentError( > >> > "SQL expression object expected, got object of type %r " > >> > "instead" % type(element) > >> > ) > >> > > >> > This exception is not raised if I directly query genome's column name > such as created_date or id. > >> > > >> > I am wondering 1) could the column name and property be used > interchangeably in some way? Or say how could to query a table's property > in the way of querying a table's column? 2) what are some significant > differences between table's column name and property? > >> > > >> > Thanks. > >> > > >> > > >> > > >> > > >> > -- > >> > SQLAlchemy - > >> > The Python SQL Toolkit and Object Relational Mapper > >> > > >> > http://www.sqlalchemy.org/ > >> > > >> > To post example code, please provide an MCVE: Minimal, Complete, and > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > >> > --- > >> > You received this message because you are subscribed to the Google > Groups "sqlalchemy" group. > >> > To unsubscribe from this group and stop receiving emails from it, > send an email to sqlalchemy+...@googlegroups.com. > >> > To view this discussion on the web visit > https://groups.google.com/d/msgid/sqlalchemy/7f03c9bb-9324-4e3e-8aea-cd0d46f9021bn%40googlegroups.com > . > > > > -- > > SQLAlchemy - > > The Python SQL Toolkit and Object Relational Mapper > > > > http://www.sqlalchemy.org/ > > > > To post example code, please provide an MCVE: Minimal, Complete, and > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > > --- > > You received this message because you are subscribed to the Google > Groups "sqlalchemy" group. > > To unsubscribe from this group and stop receiving emails from it, send > an email to sqlalchemy+...@googlegroups.com. > > To view this discussion on the web visit > https://groups.google.com/d/msgid/sqlalchemy/2fbf2d83-6865-4b9b-8db6-cb5f60e0eaffn%40googlegroups.com > . > -- SQLAlchemy - The Python SQL Toolkit and Object Relational Mapper http://www.sqlalchemy.org/ To post example code, please provide an MCVE: Minimal, Complete, and Verifiable Example. See http://stackoverflow.com/help/mcve for a full description. --- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sqlalchemy/3255fd36-2eb8-4b4a-a4c0-00e289450d74n%40googlegroups.com.
