Also this didn't work for me:
print(session.query(Jobmst)
.values(Jobmst.jobmst_type,
Jobmst.jobmst_name)
.first()
)
yields:
AttributeError: 'generator' object has no attribute 'first'
Swapping first to earlier in the chain like so:
print(session.query(Jobmst).first()
.values(Jobmst.jobmst_type,
Jobmst.jobmst_name)
)
yields:
AttributeError: 'Jobmst' object has no attribute 'values'
I get confused as well, thinking that *columns (from here
<http://docs.sqlalchemy.org/en/latest/orm/query.html#sqlalchemy.orm.query.Query.values>)
infers a list of some kind.
So if I don't have a columns variable assigned to a list, I should be able
to embed one directly with this sort of syntax values([c1,c2])
But you indicate something like values(c1,c2).
So that confuses me as a newbie to Python (my background being
predominantly Java, Groovy, Typescript, Javascript, Angular 2-4, Ionic 2-3).
The * prefix immediately clicked for my from somewhere else. Maybe
academically from reading about C++.. Something like a pointer to the whole
array.
I've been brushing up on things like *args *kwargs too - so understand
their purpose.
Duck typing, passing parameters as a dictionary is known to me from Groovy.
It still confounds me though knowing what type to pass in the values().
Have been reading here <https://stackoverflow.com/a/21384492/495157> about
it:
On Friday, 9 February 2018 09:48:51 UTC, Jeremy Flowers wrote:
>
> I was thinking about this overnight..
> Do *values* relates specifically to inserts and updates, not
> selects/deletes perhaps, which would correlate to SQL syntax.
> If, it would make sense to indicate that in the documentation
>
> On Thursday, 8 February 2018 20:29:45 UTC, Jeremy Flowers wrote:
>>
>> I've seen you can do things like this:
>> fields = ['jobmst_type', 'jobmst_name']
>> print(session.query(Jobmst).options(load_only(*fields)).first())
>>
>> But according to the documentation, you should be able to do something
>> with Query values()
>> <http://docs.sqlalchemy.org/en/latest/orm/query.html#sqlalchemy.orm.query.Query.values>
>>
>> too.
>> But once again I seem to be dumbfounded by the syntatic sugar.
>>
>> What data type does the list of values need?
>> *Is there a way to introspect that ahead of time?*
>>
>> Thought I was onto something with *.base_columns*, but that didn't work
>> either...
>>
>> I ended up with something like an instrumentalAttributes mismatch.
>> print(session.query(Jobmst)
>> .values([Jobmst.jobmst_type.base_columns,
>> Jobmst.jobmst_name.base_columns
>> ])
>> .first()
>> )
>>
>> sqlalchemy.exc.InvalidRequestError: SQL expression, column, or mapped
>> entity expected - got '[{Column('jobmst_type', Numeric(scale=0,
>> asdecimal=False), table=<jobmst>, nullable=False)}, {Column('jobmst_name',
>> String(length=256), table=<jobmst>, nullable=False)}]'
>>
>> BTW: I'm aware of querying with things like query(Jobmst.jobmst_type,
>> Jobmst.jobmst_name) too - but looking to understand what values expects.
>> Mike, Can documentation not specify type?
>>
>
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