is NamedTuple supported?

[chrisemke]

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Example Code

from typing import NamedTuple
from uuid import UUID

from pydantic import PositiveInt
from sqlmodel import Field, SQLModel


class Coordinates(NamedTuple):
    latitude: float
    longitude: float
    altitude: float

class Address(SQLModel, table=True):
    id: UUID | None = Field(default=None, primary_key=True)
    zipcode: PositiveInt
    coordinates: Coordinates | None = None

Description

Here's the error when I try creating the model with sqlmodel:

Traceback (most recent call last):
  File "/home/krisque/Personal_Projects/jacobson/main.py", line 13, in <module>
    class Address(SQLModel, table=True):
  File "/home/krisque/.pyenv/versions/3.12.2/lib/python3.12/site-packages/sqlmodel/main.py", line 474, in __new__
    col = get_column_from_field(v)
          ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/krisque/.pyenv/versions/3.12.2/lib/python3.12/site-packages/sqlmodel/main.py", line 618, in get_column_from_field
    sa_type = get_sqlalchemy_type(field)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/krisque/.pyenv/versions/3.12.2/lib/python3.12/site-packages/sqlmodel/main.py", line 607, in get_sqlalchemy_type
    raise ValueError(f"{type_} has no matching SQLAlchemy type")
ValueError: <class '__main__.Coordinates'> has no matching SQLAlchemy type

but on pydantic I used to work like this:

from typing import NamedTuple
from uuid import UUID

from pydantic import BaseModel, PositiveInt


class Coordinates(NamedTuple):
    latitude: float
    longitude: float
    altitude: float


class Address(BaseModel):
    id: UUID
    zipcode: PositiveInt
    coordinates: Coordinates | None = None

Is there any way to make this NamedTuple class work?

Operating System

Linux

Operating System Details

No response

SQLModel Version

0.0.16

Python Version

Python 3.12.2

Additional Context

No response

[motey]

Hi, had the same Question and it seems to work when you declare the column as JSON via Field(sa_column=Column(JSON)...
But there is one caveat; The value read from database is not a named tuple anymore but a list. One could start a conversation if that is a bug or wanted behavior or technical unavoidable behavior.. i dont know
Heres my test code, based on yours, that may help you:

from typing import NamedTuple
import uuid

from pydantic import PositiveInt
from sqlmodel import Field, SQLModel, create_engine, Session, select, Column, JSON

engine = create_engine(url="sqlite:///./testdb.sqlite")

class Coordinates(NamedTuple):
    latitude: float
    longitude: float
    altitude: float

class Address(SQLModel, table=True):
    id: uuid.UUID | None = Field(default_factory=uuid.uuid4, primary_key=True)
    zipcode: PositiveInt
    coordinates: Coordinates = Field(sa_column=Column(JSON))

SQLModel.metadata.create_all(engine)
coordinates = Coordinates(1.2, 1.3, 1.4)
coordinates_from_db = None

# Lets write an address with our NamedTuple coordinates into the DB
with Session(engine) as s:
    s.add(Address(zipcode="55252", coordinates=Coordinates(1.2, 1.3, 1.4)))
    s.commit()

# And now lets it read it from the DB
with Session(engine) as s:
    adr = s.exec(select(Address)).first()
    coordinates_from_db = adr.coordinates

# Now we compare our NamedTuple coordinates with the stuff that came from the DB
print("FROM MEM", type(coordinates), coordinates)
# > FROM MEM <class '__main__.named_tuple_as_db_col.<locals>.Coordinates'> Coordinates(latitude=1.2, longitude=1.3, altitude=1.4)
print("FROM DB", type(coordinates_from_db), coordinates_from_db)
# > FROM DB <class 'list'> [1.2, 1.3, 1.4]
print("Is it the same?", coordinates == coordinates_from_db)
# > False
print(
    "is it the same if cast the result back into coordinates?",
    Coordinates(*coordinates_from_db) == coordinates,
)
# > True
# Yay!

# Although the type of `coordinates_from_db` is a `list` we can use it to write coordinates into the database
with Session(engine) as s:
    # This works!
    s.add(Address(zipcode="55253", coordinates=coordinates_from_db))
    s.commit()