You are f****ing awesome Mike. Thanks for the answer and the links, I will dive into it tomorrow first thing in the morning.
Le jeu. 6 juil. 2023 à 19:27, Mike Bayer < mike_not_on_goo...@zzzcomputing.com> a écrit : > > > On Thu, Jul 6, 2023, at 1:21 PM, Pierre Massé wrote: > > Dear all, > > I am currently working on implementing UUID as primary keys in my database. > > I have come across an issue that I cannot find an explanation for: using > the `sqlalchemy.Uuid` type in declarative mapping yields different results > at initialization. I sometimes get the following error: > > *"The type provided inside the 'id' attribute Mapped annotation is the > SQLAlchemy type <class 'sqlalchemy.sql.sqltypes.Uuid'>. Expected a Python > type instead"* > > > this message is referring to the difference between *Python* types and > *SQLAlchemy* types. A SQLAlchemy type is like "sqlalchemy.Uuid" as you are > using. The Python type is the Python UUID type: > https://docs.python.org/3/library/uuid.html#uuid.UUID > > the default lookup is documented here: > https://docs.sqlalchemy.org/en/20/orm/declarative_tables.html#mapped-column-derives-the-datatype-and-nullability-from-the-mapped-annotation > > so you would want > > import uuid > > class XYZ(...): > # ... > > id: Mapped[uuid.UUID] = mapped_column(...) > > > > > > > > > I have a Caregiver table, for which id is a PostgreSQL UUID, and a Match > Event table holding 2 fields which use the Caregiver id as foreign key. > Those 2 fields are PostgreSQL UUID as well. > > If my classes definitions are as follow, the initialization runs smoothly, > as well as inserts in the Match Event table: > > from sqlalchemy import ( > ForeignKey, > Uuid, > ) > from sqlalchemy.orm import ( > Mapped, > mapped_column, > relationship, > ) > > class MatchEventOrm(Base): > __tablename__ = "match_event" > > id: Mapped[int] = mapped_column(primary_key=True) > subject_caregiver_id: Mapped[Uuid] = mapped_column( > ForeignKey("caregiver.id") > ) > object_caregiver_id: Mapped[Uuid] = mapped_column( > ForeignKey("caregiver.id") > ) > subject_caregiver: Mapped["CaregiverOrm"] = relationship( > back_populates="match_event_subject_of", > foreign_keys=[subject_caregiver_id], > ) > object_caregiver: Mapped["CaregiverOrm"] = relationship( > back_populates="match_event_object_of", > foreign_keys=[object_caregiver_id], > ) > > class CaregiverOrm(Base): > __tablename__ = "caregiver" > > id: Mapped[*str*] = mapped_column(primary_key=True) > uid: Mapped[str] > user_email: Mapped[str] > > ... > > > > However, if I change to the following: > from sqlalchemy import ( > ForeignKey, > Uuid, > ) > from sqlalchemy.orm import ( > Mapped, > mapped_column, > relationship, > ) > > class MatchEventOrm(Base): > __tablename__ = "match_event" > > id: Mapped[int] = mapped_column(primary_key=True) > subject_caregiver_id: Mapped[Uuid] = mapped_column( > ForeignKey("caregiver.id") > ) > object_caregiver_id: Mapped[Uuid] = mapped_column( > ForeignKey("caregiver.id") > ) > subject_caregiver: Mapped["CaregiverOrm"] = relationship( > back_populates="match_event_subject_of", > foreign_keys=[subject_caregiver_id], > ) > object_caregiver: Mapped["CaregiverOrm"] = relationship( > back_populates="match_event_object_of", > foreign_keys=[object_caregiver_id], > ) > > class CaregiverOrm(Base): > __tablename__ = "caregiver" > > id: Mapped[*Uuid*] = mapped_column(primary_key=True) > uid: Mapped[str] > user_email: Mapped[str] > > ... > > > I get the aforementioned error message. > > I may be using type annotations wrong, any insight on what I am doing > wrong would be welcome. > > Thanks a lot for your support. > > Regards, > > Pierre > > > > -- > 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. 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