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 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 wrote:
>> >
>> > Hi there,
>> >
>> > I got a problem about 'sqlalchemy.exc.ArgumentError: SQL expression object
>> > expected, got object of type 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.
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>> > 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.
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--
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.
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