Mike, thank you for elaborating, that helps a lot! Yes, I meant a transient
or pending
<https://docs.sqlalchemy.org/en/14/orm/session_state_management.html#quickie-intro-to-object-states>
object above, you’re correct.
To make sure I understand correctly: it’s ok to declare
deleted_at: Mapped[Optional[datetime.datetime]] =
Column(sqlalchemy.DateTime, nullable=True)
or
id: Mapped[uuid.UUID] =
Column(sqlalchemy.dialects.postgresql.UUID(as_uuid=True), primary_key=True,
default=uuid.uuid4)
where the RHS declares the column’s type by means of a SQLA type and the
LHS’s type a “*mapped”* stdlib Python type? It works here because the
column’s type actually is implemented by means of the LHS stdlib type. I
also noticed that I can omit e.g. Mapped[uuid.UUID] and in some cases mypy
is still able to infer the correct type.
Much thanks,
Jens
On Monday, January 17, 2022 at 1:04:46 AM UTC+10 Mike Bayer wrote:
>
>
> On Sat, Jan 15, 2022, at 3:34 PM, [email protected] wrote:
>
> Hello Mike,
>
> Yes that’s using the plugin:
> sqlalchemy[mypy,postgresql_psycopg2binary]==1.4.29 I changed the function
> declaration to this:
>
> @staticmethod
> def create(dbsession: Session, name: str, id_:
> typing.Union[uuid.UUID, sqlalchemy.dialects.postgresql.base.UUID] = None):
>
> and it seems to work. In a similar vain, how do I manage the types of
> mapped and unmapped objects? Following the above example:
>
> user = User(dbsession, "Joe Black")
>
> returns an unmapped, simple User object. Now suppose I have another
> existing, mapped User object and would like to assign that newly created
> unmapped user:
>
> other_user.spouse = user
>
> which creates the following error:
>
> error: Argument "spouse" to "User" has incompatible type "User"; expected
> "Mapped[Any]" [arg-type]
>
>
> if the User class is unmapped, you wouldn't be assigning it to a
> relationship attribute like that.
>
> I think what you might mean is that you have a User object that is what we
> call "transient", meaning, it's not yet persisted with any Session.
>
> again, you would want to set up the relationship attribute with a more
> specific annotation:
>
> class User(...):
> # ...
> spouse: Mapped[User] = relationship("User", ...)
>
>
> background on this in terms of the plugin is at
> https://docs.sqlalchemy.org/en/14/orm/extensions/mypy.html#mapping-relationships
>
>
>
> Declaring that column with:
>
> spouse: typing.Union[Mapped[User], User] = relationship("User",
> back_populates="spouse", uselist=False)
> seems to work; I just want to make sure that that’s a recommended way of
> going about this? Should I always declare a type as a Union between a
> mapped and unmapped same class?
>
>
> no that's not correct. The User class is "mapped" at the class level.
> you would only need one directive or the other (one of Mapped[User] or
> User) when using the Mypy plugin.
>
>
>
>
>
>
> Other than following the migration guide
> <https://docs.sqlalchemy.org/en/14/changelog/migration_20.html>, I
> haven’t looked into SQLA2
> <https://github.com/sqlalchemy/sqlalchemy/projects/3>.
> Jens
>
>
> On Thursday, January 13, 2022 at 11:52:18 PM UTC+10 Mike Bayer wrote:
>
>
> is this with the SQLAlchemy Mypy plugin? current status is for 2.0 we
> are looking to move away from the plugin model and pretty much change how
> these things work. Otherwise if this is with the plugin, you would use
> "id: Mapped[uuid.UUID] = ..."
>
>
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