1from typing import List
2from typing import Optional
3
4from sqlalchemy import Column
5from sqlalchemy import ForeignKey
6from sqlalchemy import Integer
7from sqlalchemy import select
8from sqlalchemy import String
9from sqlalchemy.orm import declarative_base
10from sqlalchemy.orm import Mapped
11from sqlalchemy.orm import relationship
12
13Base = declarative_base()
14
15
16class User(Base):
17    __tablename__ = "user"
18
19    id = Column(Integer, primary_key=True)
20    name = Column(String)
21
22    addresses: Mapped[List["Address"]] = relationship(
23        "Address", back_populates="user"
24    )
25
26    @property
27    def some_property(self) -> List[Optional[int]]:
28        return [i.id for i in self.addresses]
29
30
31class Address(Base):
32    __tablename__ = "address"
33
34    id = Column(Integer, primary_key=True)
35    user_id: int = Column(ForeignKey("user.id"))
36
37    user: "User" = relationship("User", back_populates="addresses")
38
39    @property
40    def some_other_property(self) -> Optional[str]:
41        return self.user.name
42
43
44# it's in the constructor, correct type
45u1 = User(addresses=[Address()])
46
47# knows it's an iterable
48[x for x in u1.addresses]
49
50# knows it's Mapped
51stmt = select(User).where(User.addresses.any(id=5))
52