Daten löschen - DELETE¶

Nun löschen wir einige Daten mit SQLModel.

Weiter mit vorherigem Code¶

Wie zuvor setzen wir dort fort, wo wir mit dem vorherigen Code aufgehört haben.

👀 Vorschau der vollständigen Datei

Python 3.10+

from sqlmodel import Field, Session, SQLModel, create_engine, select


class Hero(SQLModel, table=True):
    id: int | None = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    secret_name: str
    age: int | None = Field(default=None, index=True)


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

engine = create_engine(sqlite_url, echo=True)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


def create_heroes():
    hero_1 = Hero(name="Deadpond", secret_name="Dive Wilson")
    hero_2 = Hero(name="Spider-Boy", secret_name="Pedro Parqueador")
    hero_3 = Hero(name="Rusty-Man", secret_name="Tommy Sharp", age=48)
    hero_4 = Hero(name="Tarantula", secret_name="Natalia Roman-on", age=32)
    hero_5 = Hero(name="Black Lion", secret_name="Trevor Challa", age=35)
    hero_6 = Hero(name="Dr. Weird", secret_name="Steve Weird", age=36)
    hero_7 = Hero(name="Captain North America", secret_name="Esteban Rogelios", age=93)

    with Session(engine) as session:
        session.add(hero_1)
        session.add(hero_2)
        session.add(hero_3)
        session.add(hero_4)
        session.add(hero_5)
        session.add(hero_6)
        session.add(hero_7)

        session.commit()


def update_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Boy")
        results = session.exec(statement)
        hero_1 = results.one()
        print("Hero 1:", hero_1)

        statement = select(Hero).where(Hero.name == "Captain North America")
        results = session.exec(statement)
        hero_2 = results.one()
        print("Hero 2:", hero_2)

        hero_1.age = 16
        hero_1.name = "Spider-Youngster"
        session.add(hero_1)

        hero_2.name = "Captain North America Except Canada"
        hero_2.age = 110
        session.add(hero_2)

        session.commit()
        session.refresh(hero_1)
        session.refresh(hero_2)

        print("Updated hero 1:", hero_1)
        print("Updated hero 2:", hero_2)


def main():
    create_db_and_tables()
    create_heroes()
    update_heroes()


if __name__ == "__main__":
    main()

🤓 Andere Versionen und Varianten

Python 3.8+

from typing import Optional

from sqlmodel import Field, Session, SQLModel, create_engine, select


class Hero(SQLModel, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    secret_name: str
    age: Optional[int] = Field(default=None, index=True)


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

engine = create_engine(sqlite_url, echo=True)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


def create_heroes():
    hero_1 = Hero(name="Deadpond", secret_name="Dive Wilson")
    hero_2 = Hero(name="Spider-Boy", secret_name="Pedro Parqueador")
    hero_3 = Hero(name="Rusty-Man", secret_name="Tommy Sharp", age=48)
    hero_4 = Hero(name="Tarantula", secret_name="Natalia Roman-on", age=32)
    hero_5 = Hero(name="Black Lion", secret_name="Trevor Challa", age=35)
    hero_6 = Hero(name="Dr. Weird", secret_name="Steve Weird", age=36)
    hero_7 = Hero(name="Captain North America", secret_name="Esteban Rogelios", age=93)

    with Session(engine) as session:
        session.add(hero_1)
        session.add(hero_2)
        session.add(hero_3)
        session.add(hero_4)
        session.add(hero_5)
        session.add(hero_6)
        session.add(hero_7)

        session.commit()


def update_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Boy")
        results = session.exec(statement)
        hero_1 = results.one()
        print("Hero 1:", hero_1)

        statement = select(Hero).where(Hero.name == "Captain North America")
        results = session.exec(statement)
        hero_2 = results.one()
        print("Hero 2:", hero_2)

        hero_1.age = 16
        hero_1.name = "Spider-Youngster"
        session.add(hero_1)

        hero_2.name = "Captain North America Except Canada"
        hero_2.age = 110
        session.add(hero_2)

        session.commit()
        session.refresh(hero_1)
        session.refresh(hero_2)

        print("Updated hero 1:", hero_1)
        print("Updated hero 2:", hero_2)


def main():
    create_db_and_tables()
    create_heroes()
    update_heroes()


if __name__ == "__main__":
    main()

Denken Sie daran, die Datei database.db zu löschen, bevor Sie die Beispiele ausführen, um die gleichen Ergebnisse zu erzielen.

Löschen mit SQL¶

Dieser Spider-Youngster wird zu seltsam, also löschen wir ihn einfach.

Aber keine Sorge, wir werden ihn später mit einer neuen Geschichte neu starten. 😅

Sehen wir uns an, wie man ihn mit SQL löscht

DELETE
FROM hero
WHERE name = "Spider-Youngster"

Das bedeutet, mehr oder weniger

Hallo SQL-Datenbank 👋, ich möchte Zeilen DELETE (löschen) FROM (aus) der Tabelle namens hero.

Bitte löschen Sie alle Zeilen WHERE (wo) der Wert der Spalte name gleich "Spider-Youngster" ist.

Denken Sie daran, dass bei der Verwendung einer SELECT-Anweisung die Form lautet

SELECT [some stuff here]
FROM [name of a table here]
WHERE [some condition here]

DELETE ist sehr ähnlich, und wieder verwenden wir FROM, um die Tabelle anzugeben, mit der gearbeitet werden soll, und wir verwenden WHERE, um die Bedingung anzugeben, die zum Abgleichen der zu löschenden Zeilen verwendet werden soll.

Sie können dies in DB Browser for SQLite ausprobieren

Beachten Sie, dass DELETE zum Löschen ganzer Zeilen dient, nicht einzelner Werte in einer Zeile.

Wenn Sie einen einzelnen Wert in einer Spalte "löschen" möchten, während Sie die Zeile beibehalten, würden Sie stattdessen die Zeile aktualisieren, wie im vorherigen Kapitel erklärt, indem Sie den spezifischen Wert der Spalte in dieser Zeile auf NULL (in Python auf None) setzen.

Nun löschen wir mit SQLModel.

Um die gleichen Ergebnisse zu erzielen, löschen Sie die Datei database.db, bevor Sie die Beispiele ausführen.

Aus der Datenbank lesen¶

Wir beginnen damit, den Helden "Spider-Youngster" auszuwählen, den wir im vorherigen Kapitel aktualisiert haben. Diesen werden wir löschen.

Python 3.10+

# Code above omitted 👆

def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.one()
        print("Hero: ", hero)

# Code below omitted 👇

👀 Vorschau der vollständigen Datei

Python 3.10+

from sqlmodel import Field, Session, SQLModel, create_engine, select


class Hero(SQLModel, table=True):
    id: int | None = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    secret_name: str
    age: int | None = Field(default=None, index=True)


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

engine = create_engine(sqlite_url, echo=True)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


def create_heroes():
    hero_1 = Hero(name="Deadpond", secret_name="Dive Wilson")
    hero_2 = Hero(name="Spider-Boy", secret_name="Pedro Parqueador")
    hero_3 = Hero(name="Rusty-Man", secret_name="Tommy Sharp", age=48)
    hero_4 = Hero(name="Tarantula", secret_name="Natalia Roman-on", age=32)
    hero_5 = Hero(name="Black Lion", secret_name="Trevor Challa", age=35)
    hero_6 = Hero(name="Dr. Weird", secret_name="Steve Weird", age=36)
    hero_7 = Hero(name="Captain North America", secret_name="Esteban Rogelios", age=93)

    with Session(engine) as session:
        session.add(hero_1)
        session.add(hero_2)
        session.add(hero_3)
        session.add(hero_4)
        session.add(hero_5)
        session.add(hero_6)
        session.add(hero_7)

        session.commit()


def update_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Boy")
        results = session.exec(statement)
        hero_1 = results.one()
        print("Hero 1:", hero_1)

        statement = select(Hero).where(Hero.name == "Captain North America")
        results = session.exec(statement)
        hero_2 = results.one()
        print("Hero 2:", hero_2)

        hero_1.age = 16
        hero_1.name = "Spider-Youngster"
        session.add(hero_1)

        hero_2.name = "Captain North America Except Canada"
        hero_2.age = 110
        session.add(hero_2)

        session.commit()
        session.refresh(hero_1)
        session.refresh(hero_2)

        print("Updated hero 1:", hero_1)
        print("Updated hero 2:", hero_2)


def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.one()
        print("Hero: ", hero)

        session.delete(hero)
        session.commit()

        print("Deleted hero:", hero)

        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.first()

        if hero is None:
            print("There's no hero named Spider-Youngster")


def main():
    create_db_and_tables()
    create_heroes()
    update_heroes()
    delete_heroes()


if __name__ == "__main__":
    main()

🤓 Andere Versionen und Varianten

Python 3.8+

from typing import Optional

from sqlmodel import Field, Session, SQLModel, create_engine, select


class Hero(SQLModel, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    secret_name: str
    age: Optional[int] = Field(default=None, index=True)


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

engine = create_engine(sqlite_url, echo=True)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


def create_heroes():
    hero_1 = Hero(name="Deadpond", secret_name="Dive Wilson")
    hero_2 = Hero(name="Spider-Boy", secret_name="Pedro Parqueador")
    hero_3 = Hero(name="Rusty-Man", secret_name="Tommy Sharp", age=48)
    hero_4 = Hero(name="Tarantula", secret_name="Natalia Roman-on", age=32)
    hero_5 = Hero(name="Black Lion", secret_name="Trevor Challa", age=35)
    hero_6 = Hero(name="Dr. Weird", secret_name="Steve Weird", age=36)
    hero_7 = Hero(name="Captain North America", secret_name="Esteban Rogelios", age=93)

    with Session(engine) as session:
        session.add(hero_1)
        session.add(hero_2)
        session.add(hero_3)
        session.add(hero_4)
        session.add(hero_5)
        session.add(hero_6)
        session.add(hero_7)

        session.commit()


def update_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Boy")
        results = session.exec(statement)
        hero_1 = results.one()
        print("Hero 1:", hero_1)

        statement = select(Hero).where(Hero.name == "Captain North America")
        results = session.exec(statement)
        hero_2 = results.one()
        print("Hero 2:", hero_2)

        hero_1.age = 16
        hero_1.name = "Spider-Youngster"
        session.add(hero_1)

        hero_2.name = "Captain North America Except Canada"
        hero_2.age = 110
        session.add(hero_2)

        session.commit()
        session.refresh(hero_1)
        session.refresh(hero_2)

        print("Updated hero 1:", hero_1)
        print("Updated hero 2:", hero_2)


def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.one()
        print("Hero: ", hero)

        session.delete(hero)
        session.commit()

        print("Deleted hero:", hero)

        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.first()

        if hero is None:
            print("There's no hero named Spider-Youngster")


def main():
    create_db_and_tables()
    create_heroes()
    update_heroes()
    delete_heroes()


if __name__ == "__main__":
    main()

Da dies eine neue Funktion delete_heroes() ist, werden wir sie auch zur Funktion main() hinzufügen, damit wir sie beim Ausführen des Programms über die Befehlszeile aufrufen.

Python 3.10+

# Code above omitted 👆

def main():
    create_db_and_tables()
    create_heroes()
    update_heroes()
    delete_heroes()


if __name__ == "__main__":
    main()

👀 Vorschau der vollständigen Datei

Python 3.10+

from sqlmodel import Field, Session, SQLModel, create_engine, select


class Hero(SQLModel, table=True):
    id: int | None = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    secret_name: str
    age: int | None = Field(default=None, index=True)


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

engine = create_engine(sqlite_url, echo=True)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


def create_heroes():
    hero_1 = Hero(name="Deadpond", secret_name="Dive Wilson")
    hero_2 = Hero(name="Spider-Boy", secret_name="Pedro Parqueador")
    hero_3 = Hero(name="Rusty-Man", secret_name="Tommy Sharp", age=48)
    hero_4 = Hero(name="Tarantula", secret_name="Natalia Roman-on", age=32)
    hero_5 = Hero(name="Black Lion", secret_name="Trevor Challa", age=35)
    hero_6 = Hero(name="Dr. Weird", secret_name="Steve Weird", age=36)
    hero_7 = Hero(name="Captain North America", secret_name="Esteban Rogelios", age=93)

    with Session(engine) as session:
        session.add(hero_1)
        session.add(hero_2)
        session.add(hero_3)
        session.add(hero_4)
        session.add(hero_5)
        session.add(hero_6)
        session.add(hero_7)

        session.commit()


def update_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Boy")
        results = session.exec(statement)
        hero_1 = results.one()
        print("Hero 1:", hero_1)

        statement = select(Hero).where(Hero.name == "Captain North America")
        results = session.exec(statement)
        hero_2 = results.one()
        print("Hero 2:", hero_2)

        hero_1.age = 16
        hero_1.name = "Spider-Youngster"
        session.add(hero_1)

        hero_2.name = "Captain North America Except Canada"
        hero_2.age = 110
        session.add(hero_2)

        session.commit()
        session.refresh(hero_1)
        session.refresh(hero_2)

        print("Updated hero 1:", hero_1)
        print("Updated hero 2:", hero_2)


def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.one()
        print("Hero: ", hero)

        session.delete(hero)
        session.commit()

        print("Deleted hero:", hero)

        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.first()

        if hero is None:
            print("There's no hero named Spider-Youngster")


def main():
    create_db_and_tables()
    create_heroes()
    update_heroes()
    delete_heroes()


if __name__ == "__main__":
    main()

🤓 Andere Versionen und Varianten

Python 3.8+

from typing import Optional

from sqlmodel import Field, Session, SQLModel, create_engine, select


class Hero(SQLModel, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    secret_name: str
    age: Optional[int] = Field(default=None, index=True)


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

engine = create_engine(sqlite_url, echo=True)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


def create_heroes():
    hero_1 = Hero(name="Deadpond", secret_name="Dive Wilson")
    hero_2 = Hero(name="Spider-Boy", secret_name="Pedro Parqueador")
    hero_3 = Hero(name="Rusty-Man", secret_name="Tommy Sharp", age=48)
    hero_4 = Hero(name="Tarantula", secret_name="Natalia Roman-on", age=32)
    hero_5 = Hero(name="Black Lion", secret_name="Trevor Challa", age=35)
    hero_6 = Hero(name="Dr. Weird", secret_name="Steve Weird", age=36)
    hero_7 = Hero(name="Captain North America", secret_name="Esteban Rogelios", age=93)

    with Session(engine) as session:
        session.add(hero_1)
        session.add(hero_2)
        session.add(hero_3)
        session.add(hero_4)
        session.add(hero_5)
        session.add(hero_6)
        session.add(hero_7)

        session.commit()


def update_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Boy")
        results = session.exec(statement)
        hero_1 = results.one()
        print("Hero 1:", hero_1)

        statement = select(Hero).where(Hero.name == "Captain North America")
        results = session.exec(statement)
        hero_2 = results.one()
        print("Hero 2:", hero_2)

        hero_1.age = 16
        hero_1.name = "Spider-Youngster"
        session.add(hero_1)

        hero_2.name = "Captain North America Except Canada"
        hero_2.age = 110
        session.add(hero_2)

        session.commit()
        session.refresh(hero_1)
        session.refresh(hero_2)

        print("Updated hero 1:", hero_1)
        print("Updated hero 2:", hero_2)


def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.one()
        print("Hero: ", hero)

        session.delete(hero)
        session.commit()

        print("Deleted hero:", hero)

        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.first()

        if hero is None:
            print("There's no hero named Spider-Youngster")


def main():
    create_db_and_tables()
    create_heroes()
    update_heroes()
    delete_heroes()


if __name__ == "__main__":
    main()

Dies gibt denselben vorhandenen Helden Spider-Youngster aus

$ python app.py

// Some boilerplate and previous output omitted 😉

// The SELECT with WHERE
INFO Engine BEGIN (implicit)
INFO Engine SELECT hero.id, hero.name, hero.secret_name, hero.age
FROM hero
WHERE hero.name = ?
INFO Engine [no key 0.00011s] ('Spider-Youngster',)

// Print the hero as obtained from the database
Hero:  name='Spider-Youngster' secret_name='Pedro Parqueador' age=16 id=2

Den Helden aus der Session löschen¶

Nun können wir, sehr ähnlich wie wir session.add() zum Hinzufügen oder Aktualisieren neuer Helden verwendet haben, session.delete() verwenden, um den Helden aus der Session zu löschen.

Python 3.10+

# Code above omitted 👆

def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.one()
        print("Hero: ", hero)

        session.delete(hero)

# Code below omitted 👇

👀 Vorschau der vollständigen Datei

Python 3.10+

from sqlmodel import Field, Session, SQLModel, create_engine, select


class Hero(SQLModel, table=True):
    id: int | None = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    secret_name: str
    age: int | None = Field(default=None, index=True)


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

engine = create_engine(sqlite_url, echo=True)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


def create_heroes():
    hero_1 = Hero(name="Deadpond", secret_name="Dive Wilson")
    hero_2 = Hero(name="Spider-Boy", secret_name="Pedro Parqueador")
    hero_3 = Hero(name="Rusty-Man", secret_name="Tommy Sharp", age=48)
    hero_4 = Hero(name="Tarantula", secret_name="Natalia Roman-on", age=32)
    hero_5 = Hero(name="Black Lion", secret_name="Trevor Challa", age=35)
    hero_6 = Hero(name="Dr. Weird", secret_name="Steve Weird", age=36)
    hero_7 = Hero(name="Captain North America", secret_name="Esteban Rogelios", age=93)

    with Session(engine) as session:
        session.add(hero_1)
        session.add(hero_2)
        session.add(hero_3)
        session.add(hero_4)
        session.add(hero_5)
        session.add(hero_6)
        session.add(hero_7)

        session.commit()


def update_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Boy")
        results = session.exec(statement)
        hero_1 = results.one()
        print("Hero 1:", hero_1)

        statement = select(Hero).where(Hero.name == "Captain North America")
        results = session.exec(statement)
        hero_2 = results.one()
        print("Hero 2:", hero_2)

        hero_1.age = 16
        hero_1.name = "Spider-Youngster"
        session.add(hero_1)

        hero_2.name = "Captain North America Except Canada"
        hero_2.age = 110
        session.add(hero_2)

        session.commit()
        session.refresh(hero_1)
        session.refresh(hero_2)

        print("Updated hero 1:", hero_1)
        print("Updated hero 2:", hero_2)


def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.one()
        print("Hero: ", hero)

        session.delete(hero)
        session.commit()

        print("Deleted hero:", hero)

        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.first()

        if hero is None:
            print("There's no hero named Spider-Youngster")


def main():
    create_db_and_tables()
    create_heroes()
    update_heroes()
    delete_heroes()


if __name__ == "__main__":
    main()

🤓 Andere Versionen und Varianten

Python 3.8+

from typing import Optional

from sqlmodel import Field, Session, SQLModel, create_engine, select


class Hero(SQLModel, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    secret_name: str
    age: Optional[int] = Field(default=None, index=True)


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

engine = create_engine(sqlite_url, echo=True)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


def create_heroes():
    hero_1 = Hero(name="Deadpond", secret_name="Dive Wilson")
    hero_2 = Hero(name="Spider-Boy", secret_name="Pedro Parqueador")
    hero_3 = Hero(name="Rusty-Man", secret_name="Tommy Sharp", age=48)
    hero_4 = Hero(name="Tarantula", secret_name="Natalia Roman-on", age=32)
    hero_5 = Hero(name="Black Lion", secret_name="Trevor Challa", age=35)
    hero_6 = Hero(name="Dr. Weird", secret_name="Steve Weird", age=36)
    hero_7 = Hero(name="Captain North America", secret_name="Esteban Rogelios", age=93)

    with Session(engine) as session:
        session.add(hero_1)
        session.add(hero_2)
        session.add(hero_3)
        session.add(hero_4)
        session.add(hero_5)
        session.add(hero_6)
        session.add(hero_7)

        session.commit()


def update_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Boy")
        results = session.exec(statement)
        hero_1 = results.one()
        print("Hero 1:", hero_1)

        statement = select(Hero).where(Hero.name == "Captain North America")
        results = session.exec(statement)
        hero_2 = results.one()
        print("Hero 2:", hero_2)

        hero_1.age = 16
        hero_1.name = "Spider-Youngster"
        session.add(hero_1)

        hero_2.name = "Captain North America Except Canada"
        hero_2.age = 110
        session.add(hero_2)

        session.commit()
        session.refresh(hero_1)
        session.refresh(hero_2)

        print("Updated hero 1:", hero_1)
        print("Updated hero 2:", hero_2)


def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.one()
        print("Hero: ", hero)

        session.delete(hero)
        session.commit()

        print("Deleted hero:", hero)

        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.first()

        if hero is None:
            print("There's no hero named Spider-Youngster")


def main():
    create_db_and_tables()
    create_heroes()
    update_heroes()
    delete_heroes()


if __name__ == "__main__":
    main()

Die Session committen¶

Um die aktuellen Änderungen in der Session zu speichern, committen Sie sie.

Dies speichert alle in der Session gespeicherten Änderungen, wie den gelöschten Helden.

Python 3.10+

# Code above omitted 👆

def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.one()
        print("Hero: ", hero)

        session.delete(hero)
        session.commit()

# Code below omitted 👇

👀 Vorschau der vollständigen Datei

Python 3.10+

from sqlmodel import Field, Session, SQLModel, create_engine, select


class Hero(SQLModel, table=True):
    id: int | None = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    secret_name: str
    age: int | None = Field(default=None, index=True)


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

engine = create_engine(sqlite_url, echo=True)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


def create_heroes():
    hero_1 = Hero(name="Deadpond", secret_name="Dive Wilson")
    hero_2 = Hero(name="Spider-Boy", secret_name="Pedro Parqueador")
    hero_3 = Hero(name="Rusty-Man", secret_name="Tommy Sharp", age=48)
    hero_4 = Hero(name="Tarantula", secret_name="Natalia Roman-on", age=32)
    hero_5 = Hero(name="Black Lion", secret_name="Trevor Challa", age=35)
    hero_6 = Hero(name="Dr. Weird", secret_name="Steve Weird", age=36)
    hero_7 = Hero(name="Captain North America", secret_name="Esteban Rogelios", age=93)

    with Session(engine) as session:
        session.add(hero_1)
        session.add(hero_2)
        session.add(hero_3)
        session.add(hero_4)
        session.add(hero_5)
        session.add(hero_6)
        session.add(hero_7)

        session.commit()


def update_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Boy")
        results = session.exec(statement)
        hero_1 = results.one()
        print("Hero 1:", hero_1)

        statement = select(Hero).where(Hero.name == "Captain North America")
        results = session.exec(statement)
        hero_2 = results.one()
        print("Hero 2:", hero_2)

        hero_1.age = 16
        hero_1.name = "Spider-Youngster"
        session.add(hero_1)

        hero_2.name = "Captain North America Except Canada"
        hero_2.age = 110
        session.add(hero_2)

        session.commit()
        session.refresh(hero_1)
        session.refresh(hero_2)

        print("Updated hero 1:", hero_1)
        print("Updated hero 2:", hero_2)


def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.one()
        print("Hero: ", hero)

        session.delete(hero)
        session.commit()

        print("Deleted hero:", hero)

        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.first()

        if hero is None:
            print("There's no hero named Spider-Youngster")


def main():
    create_db_and_tables()
    create_heroes()
    update_heroes()
    delete_heroes()


if __name__ == "__main__":
    main()

🤓 Andere Versionen und Varianten

Python 3.8+

from typing import Optional

from sqlmodel import Field, Session, SQLModel, create_engine, select


class Hero(SQLModel, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    secret_name: str
    age: Optional[int] = Field(default=None, index=True)


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

engine = create_engine(sqlite_url, echo=True)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


def create_heroes():
    hero_1 = Hero(name="Deadpond", secret_name="Dive Wilson")
    hero_2 = Hero(name="Spider-Boy", secret_name="Pedro Parqueador")
    hero_3 = Hero(name="Rusty-Man", secret_name="Tommy Sharp", age=48)
    hero_4 = Hero(name="Tarantula", secret_name="Natalia Roman-on", age=32)
    hero_5 = Hero(name="Black Lion", secret_name="Trevor Challa", age=35)
    hero_6 = Hero(name="Dr. Weird", secret_name="Steve Weird", age=36)
    hero_7 = Hero(name="Captain North America", secret_name="Esteban Rogelios", age=93)

    with Session(engine) as session:
        session.add(hero_1)
        session.add(hero_2)
        session.add(hero_3)
        session.add(hero_4)
        session.add(hero_5)
        session.add(hero_6)
        session.add(hero_7)

        session.commit()


def update_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Boy")
        results = session.exec(statement)
        hero_1 = results.one()
        print("Hero 1:", hero_1)

        statement = select(Hero).where(Hero.name == "Captain North America")
        results = session.exec(statement)
        hero_2 = results.one()
        print("Hero 2:", hero_2)

        hero_1.age = 16
        hero_1.name = "Spider-Youngster"
        session.add(hero_1)

        hero_2.name = "Captain North America Except Canada"
        hero_2.age = 110
        session.add(hero_2)

        session.commit()
        session.refresh(hero_1)
        session.refresh(hero_2)

        print("Updated hero 1:", hero_1)
        print("Updated hero 2:", hero_2)


def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.one()
        print("Hero: ", hero)

        session.delete(hero)
        session.commit()

        print("Deleted hero:", hero)

        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.first()

        if hero is None:
            print("There's no hero named Spider-Youngster")


def main():
    create_db_and_tables()
    create_heroes()
    update_heroes()
    delete_heroes()


if __name__ == "__main__":
    main()

Wie wir bereits gesehen haben, speichert .commit() auch alles andere, was zur Session hinzugefügt wurde. Dazu gehören Aktualisierungen oder erstellte Helden.

Dieses Commit nach dem Löschen des Helden erzeugt diese Ausgabe

$ python app.py

// Some boilerplate output omitted 😉

// Previous output omitted 🙈

// The SQL to update the hero in the database
INFO Engine DELETE FROM hero WHERE hero.id = ?
INFO Engine [generated in 0.00020s] (2,)
INFO Engine COMMIT

Das gelöschte Objekt ausgeben¶

Nun ist der Held aus der Datenbank gelöscht.

Wenn wir versuchen würden, ihn mit session.refresh() zu aktualisieren, würde dies eine Ausnahme auslösen, da keine Daten für diesen Helden in der Datenbank vorhanden sind.

Dennoch ist das Objekt weiterhin mit seinen Daten verfügbar, aber es ist nicht mehr mit der Session verbunden und existiert nicht mehr in der Datenbank.

Da das Objekt nicht mit der Session verbunden ist, ist es nicht als "abgelaufen" markiert, die Session kümmert sich nicht einmal mehr groß um dieses Objekt.

Deshalb enthält das Objekt immer noch seine Attribute mit den Daten darin, sodass wir es ausgeben können.

Python 3.10+

# Code above omitted 👆

def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.one()
        print("Hero: ", hero)

        session.delete(hero)
        session.commit()

        print("Deleted hero:", hero)

# Code below omitted 👇

👀 Vorschau der vollständigen Datei

Python 3.10+

from sqlmodel import Field, Session, SQLModel, create_engine, select


class Hero(SQLModel, table=True):
    id: int | None = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    secret_name: str
    age: int | None = Field(default=None, index=True)


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

engine = create_engine(sqlite_url, echo=True)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


def create_heroes():
    hero_1 = Hero(name="Deadpond", secret_name="Dive Wilson")
    hero_2 = Hero(name="Spider-Boy", secret_name="Pedro Parqueador")
    hero_3 = Hero(name="Rusty-Man", secret_name="Tommy Sharp", age=48)
    hero_4 = Hero(name="Tarantula", secret_name="Natalia Roman-on", age=32)
    hero_5 = Hero(name="Black Lion", secret_name="Trevor Challa", age=35)
    hero_6 = Hero(name="Dr. Weird", secret_name="Steve Weird", age=36)
    hero_7 = Hero(name="Captain North America", secret_name="Esteban Rogelios", age=93)

    with Session(engine) as session:
        session.add(hero_1)
        session.add(hero_2)
        session.add(hero_3)
        session.add(hero_4)
        session.add(hero_5)
        session.add(hero_6)
        session.add(hero_7)

        session.commit()


def update_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Boy")
        results = session.exec(statement)
        hero_1 = results.one()
        print("Hero 1:", hero_1)

        statement = select(Hero).where(Hero.name == "Captain North America")
        results = session.exec(statement)
        hero_2 = results.one()
        print("Hero 2:", hero_2)

        hero_1.age = 16
        hero_1.name = "Spider-Youngster"
        session.add(hero_1)

        hero_2.name = "Captain North America Except Canada"
        hero_2.age = 110
        session.add(hero_2)

        session.commit()
        session.refresh(hero_1)
        session.refresh(hero_2)

        print("Updated hero 1:", hero_1)
        print("Updated hero 2:", hero_2)


def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.one()
        print("Hero: ", hero)

        session.delete(hero)
        session.commit()

        print("Deleted hero:", hero)

        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.first()

        if hero is None:
            print("There's no hero named Spider-Youngster")


def main():
    create_db_and_tables()
    create_heroes()
    update_heroes()
    delete_heroes()


if __name__ == "__main__":
    main()

🤓 Andere Versionen und Varianten

Python 3.8+

from typing import Optional

from sqlmodel import Field, Session, SQLModel, create_engine, select


class Hero(SQLModel, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    secret_name: str
    age: Optional[int] = Field(default=None, index=True)


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

engine = create_engine(sqlite_url, echo=True)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


def create_heroes():
    hero_1 = Hero(name="Deadpond", secret_name="Dive Wilson")
    hero_2 = Hero(name="Spider-Boy", secret_name="Pedro Parqueador")
    hero_3 = Hero(name="Rusty-Man", secret_name="Tommy Sharp", age=48)
    hero_4 = Hero(name="Tarantula", secret_name="Natalia Roman-on", age=32)
    hero_5 = Hero(name="Black Lion", secret_name="Trevor Challa", age=35)
    hero_6 = Hero(name="Dr. Weird", secret_name="Steve Weird", age=36)
    hero_7 = Hero(name="Captain North America", secret_name="Esteban Rogelios", age=93)

    with Session(engine) as session:
        session.add(hero_1)
        session.add(hero_2)
        session.add(hero_3)
        session.add(hero_4)
        session.add(hero_5)
        session.add(hero_6)
        session.add(hero_7)

        session.commit()


def update_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Boy")
        results = session.exec(statement)
        hero_1 = results.one()
        print("Hero 1:", hero_1)

        statement = select(Hero).where(Hero.name == "Captain North America")
        results = session.exec(statement)
        hero_2 = results.one()
        print("Hero 2:", hero_2)

        hero_1.age = 16
        hero_1.name = "Spider-Youngster"
        session.add(hero_1)

        hero_2.name = "Captain North America Except Canada"
        hero_2.age = 110
        session.add(hero_2)

        session.commit()
        session.refresh(hero_1)
        session.refresh(hero_2)

        print("Updated hero 1:", hero_1)
        print("Updated hero 2:", hero_2)


def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.one()
        print("Hero: ", hero)

        session.delete(hero)
        session.commit()

        print("Deleted hero:", hero)

        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.first()

        if hero is None:
            print("There's no hero named Spider-Youngster")


def main():
    create_db_and_tables()
    create_heroes()
    update_heroes()
    delete_heroes()


if __name__ == "__main__":
    main()

Dies gibt Folgendes aus

$ python app.py

// Some boilerplate output omitted 😉

// Previous output omitted 🙈

// Print the deleted hero
Deleted hero: name='Spider-Youngster' secret_name='Pedro Parqueador' age=16 id=2

Die gleiche Zeile in der Datenbank abfragen¶

Um zu bestätigen, ob er gelöscht wurde, fragen wir nun erneut die Datenbank ab, mit demselben Namen "Spider-Youngster".

Python 3.10+

# Code above omitted 👆

def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.one()
        print("Hero: ", hero)

        session.delete(hero)
        session.commit()

        print("Deleted hero:", hero)

        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.first()

# Code below omitted 👇

👀 Vorschau der vollständigen Datei

Python 3.10+

from sqlmodel import Field, Session, SQLModel, create_engine, select


class Hero(SQLModel, table=True):
    id: int | None = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    secret_name: str
    age: int | None = Field(default=None, index=True)


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

engine = create_engine(sqlite_url, echo=True)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


def create_heroes():
    hero_1 = Hero(name="Deadpond", secret_name="Dive Wilson")
    hero_2 = Hero(name="Spider-Boy", secret_name="Pedro Parqueador")
    hero_3 = Hero(name="Rusty-Man", secret_name="Tommy Sharp", age=48)
    hero_4 = Hero(name="Tarantula", secret_name="Natalia Roman-on", age=32)
    hero_5 = Hero(name="Black Lion", secret_name="Trevor Challa", age=35)
    hero_6 = Hero(name="Dr. Weird", secret_name="Steve Weird", age=36)
    hero_7 = Hero(name="Captain North America", secret_name="Esteban Rogelios", age=93)

    with Session(engine) as session:
        session.add(hero_1)
        session.add(hero_2)
        session.add(hero_3)
        session.add(hero_4)
        session.add(hero_5)
        session.add(hero_6)
        session.add(hero_7)

        session.commit()


def update_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Boy")
        results = session.exec(statement)
        hero_1 = results.one()
        print("Hero 1:", hero_1)

        statement = select(Hero).where(Hero.name == "Captain North America")
        results = session.exec(statement)
        hero_2 = results.one()
        print("Hero 2:", hero_2)

        hero_1.age = 16
        hero_1.name = "Spider-Youngster"
        session.add(hero_1)

        hero_2.name = "Captain North America Except Canada"
        hero_2.age = 110
        session.add(hero_2)

        session.commit()
        session.refresh(hero_1)
        session.refresh(hero_2)

        print("Updated hero 1:", hero_1)
        print("Updated hero 2:", hero_2)


def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.one()
        print("Hero: ", hero)

        session.delete(hero)
        session.commit()

        print("Deleted hero:", hero)

        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.first()

        if hero is None:
            print("There's no hero named Spider-Youngster")


def main():
    create_db_and_tables()
    create_heroes()
    update_heroes()
    delete_heroes()


if __name__ == "__main__":
    main()

🤓 Andere Versionen und Varianten

Python 3.8+

from typing import Optional

from sqlmodel import Field, Session, SQLModel, create_engine, select


class Hero(SQLModel, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    secret_name: str
    age: Optional[int] = Field(default=None, index=True)


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

engine = create_engine(sqlite_url, echo=True)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


def create_heroes():
    hero_1 = Hero(name="Deadpond", secret_name="Dive Wilson")
    hero_2 = Hero(name="Spider-Boy", secret_name="Pedro Parqueador")
    hero_3 = Hero(name="Rusty-Man", secret_name="Tommy Sharp", age=48)
    hero_4 = Hero(name="Tarantula", secret_name="Natalia Roman-on", age=32)
    hero_5 = Hero(name="Black Lion", secret_name="Trevor Challa", age=35)
    hero_6 = Hero(name="Dr. Weird", secret_name="Steve Weird", age=36)
    hero_7 = Hero(name="Captain North America", secret_name="Esteban Rogelios", age=93)

    with Session(engine) as session:
        session.add(hero_1)
        session.add(hero_2)
        session.add(hero_3)
        session.add(hero_4)
        session.add(hero_5)
        session.add(hero_6)
        session.add(hero_7)

        session.commit()


def update_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Boy")
        results = session.exec(statement)
        hero_1 = results.one()
        print("Hero 1:", hero_1)

        statement = select(Hero).where(Hero.name == "Captain North America")
        results = session.exec(statement)
        hero_2 = results.one()
        print("Hero 2:", hero_2)

        hero_1.age = 16
        hero_1.name = "Spider-Youngster"
        session.add(hero_1)

        hero_2.name = "Captain North America Except Canada"
        hero_2.age = 110
        session.add(hero_2)

        session.commit()
        session.refresh(hero_1)
        session.refresh(hero_2)

        print("Updated hero 1:", hero_1)
        print("Updated hero 2:", hero_2)


def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.one()
        print("Hero: ", hero)

        session.delete(hero)
        session.commit()

        print("Deleted hero:", hero)

        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.first()

        if hero is None:
            print("There's no hero named Spider-Youngster")


def main():
    create_db_and_tables()
    create_heroes()
    update_heroes()
    delete_heroes()


if __name__ == "__main__":
    main()

Hier verwenden wir results.first(), um das erste gefundene Objekt zu erhalten (falls mehrere gefunden wurden) oder None, wenn nichts gefunden wurde.

Wenn wir stattdessen results.one() verwenden würden, würde dies eine Ausnahme auslösen, da genau ein Ergebnis erwartet wird.

Und da wir diesen Helden gerade gelöscht haben, sollte dies nichts finden und wir sollten None erhalten.

Dies führt einige SQL-Befehle in der Datenbank aus und gibt Folgendes aus

$ python app.py

// Some boilerplate output omitted 😉

// Previous output omitted 🙈

// Automatically start a new transaction
INFO Engine BEGIN (implicit)

// SQL to search for the hero
INFO Engine SELECT hero.id, hero.name, hero.secret_name, hero.age
FROM hero
WHERE hero.name = ?
INFO Engine [no key 0.00013s] ('Spider-Youngster',)

Die Löschung bestätigen¶

Lassen Sie uns nun einfach bestätigen, dass tatsächlich kein Held mit diesem Namen in der Datenbank gefunden wurde.

Dies tun wir, indem wir überprüfen, ob das "erste" Element in results None ist.

Python 3.10+

# Code above omitted 👆

def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.one()
        print("Hero: ", hero)

        session.delete(hero)
        session.commit()

        print("Deleted hero:", hero)

        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.first()

        if hero is None:
            print("There's no hero named Spider-Youngster")

# Code below omitted 👇

👀 Vorschau der vollständigen Datei

Python 3.10+

from sqlmodel import Field, Session, SQLModel, create_engine, select


class Hero(SQLModel, table=True):
    id: int | None = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    secret_name: str
    age: int | None = Field(default=None, index=True)


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

engine = create_engine(sqlite_url, echo=True)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


def create_heroes():
    hero_1 = Hero(name="Deadpond", secret_name="Dive Wilson")
    hero_2 = Hero(name="Spider-Boy", secret_name="Pedro Parqueador")
    hero_3 = Hero(name="Rusty-Man", secret_name="Tommy Sharp", age=48)
    hero_4 = Hero(name="Tarantula", secret_name="Natalia Roman-on", age=32)
    hero_5 = Hero(name="Black Lion", secret_name="Trevor Challa", age=35)
    hero_6 = Hero(name="Dr. Weird", secret_name="Steve Weird", age=36)
    hero_7 = Hero(name="Captain North America", secret_name="Esteban Rogelios", age=93)

    with Session(engine) as session:
        session.add(hero_1)
        session.add(hero_2)
        session.add(hero_3)
        session.add(hero_4)
        session.add(hero_5)
        session.add(hero_6)
        session.add(hero_7)

        session.commit()


def update_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Boy")
        results = session.exec(statement)
        hero_1 = results.one()
        print("Hero 1:", hero_1)

        statement = select(Hero).where(Hero.name == "Captain North America")
        results = session.exec(statement)
        hero_2 = results.one()
        print("Hero 2:", hero_2)

        hero_1.age = 16
        hero_1.name = "Spider-Youngster"
        session.add(hero_1)

        hero_2.name = "Captain North America Except Canada"
        hero_2.age = 110
        session.add(hero_2)

        session.commit()
        session.refresh(hero_1)
        session.refresh(hero_2)

        print("Updated hero 1:", hero_1)
        print("Updated hero 2:", hero_2)


def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.one()
        print("Hero: ", hero)

        session.delete(hero)
        session.commit()

        print("Deleted hero:", hero)

        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.first()

        if hero is None:
            print("There's no hero named Spider-Youngster")


def main():
    create_db_and_tables()
    create_heroes()
    update_heroes()
    delete_heroes()


if __name__ == "__main__":
    main()

🤓 Andere Versionen und Varianten

Python 3.8+

from typing import Optional

from sqlmodel import Field, Session, SQLModel, create_engine, select


class Hero(SQLModel, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    secret_name: str
    age: Optional[int] = Field(default=None, index=True)


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

engine = create_engine(sqlite_url, echo=True)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


def create_heroes():
    hero_1 = Hero(name="Deadpond", secret_name="Dive Wilson")
    hero_2 = Hero(name="Spider-Boy", secret_name="Pedro Parqueador")
    hero_3 = Hero(name="Rusty-Man", secret_name="Tommy Sharp", age=48)
    hero_4 = Hero(name="Tarantula", secret_name="Natalia Roman-on", age=32)
    hero_5 = Hero(name="Black Lion", secret_name="Trevor Challa", age=35)
    hero_6 = Hero(name="Dr. Weird", secret_name="Steve Weird", age=36)
    hero_7 = Hero(name="Captain North America", secret_name="Esteban Rogelios", age=93)

    with Session(engine) as session:
        session.add(hero_1)
        session.add(hero_2)
        session.add(hero_3)
        session.add(hero_4)
        session.add(hero_5)
        session.add(hero_6)
        session.add(hero_7)

        session.commit()


def update_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Boy")
        results = session.exec(statement)
        hero_1 = results.one()
        print("Hero 1:", hero_1)

        statement = select(Hero).where(Hero.name == "Captain North America")
        results = session.exec(statement)
        hero_2 = results.one()
        print("Hero 2:", hero_2)

        hero_1.age = 16
        hero_1.name = "Spider-Youngster"
        session.add(hero_1)

        hero_2.name = "Captain North America Except Canada"
        hero_2.age = 110
        session.add(hero_2)

        session.commit()
        session.refresh(hero_1)
        session.refresh(hero_2)

        print("Updated hero 1:", hero_1)
        print("Updated hero 2:", hero_2)


def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.one()
        print("Hero: ", hero)

        session.delete(hero)
        session.commit()

        print("Deleted hero:", hero)

        statement = select(Hero).where(Hero.name == "Spider-Youngster")
        results = session.exec(statement)
        hero = results.first()

        if hero is None:
            print("There's no hero named Spider-Youngster")


def main():
    create_db_and_tables()
    create_heroes()
    update_heroes()
    delete_heroes()


if __name__ == "__main__":
    main()

Dies gibt Folgendes aus

$ python app.py

// Some boilerplate output omitted 😉

// Previous output omitted 🙈

// Indeed, the hero was deleted 🔥
There's no hero named Spider-Youngster

// Cleanup after the with block
INFO Engine ROLLBACK

Den Code überprüfen¶

Überprüfen wir nun den gesamten Code.

Python 3.10+Python 3.8+

from sqlmodel import Field, Session, SQLModel, create_engine, select


class Hero(SQLModel, table=True):
    id: int | None = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    secret_name: str
    age: int | None = Field(default=None, index=True)


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

engine = create_engine(sqlite_url, echo=True)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


def create_heroes():
    hero_1 = Hero(name="Deadpond", secret_name="Dive Wilson")
    hero_2 = Hero(name="Spider-Boy", secret_name="Pedro Parqueador")
    hero_3 = Hero(name="Rusty-Man", secret_name="Tommy Sharp", age=48)
    hero_4 = Hero(name="Tarantula", secret_name="Natalia Roman-on", age=32)
    hero_5 = Hero(name="Black Lion", secret_name="Trevor Challa", age=35)
    hero_6 = Hero(name="Dr. Weird", secret_name="Steve Weird", age=36)
    hero_7 = Hero(name="Captain North America", secret_name="Esteban Rogelios", age=93)

    with Session(engine) as session:
        session.add(hero_1)
        session.add(hero_2)
        session.add(hero_3)
        session.add(hero_4)
        session.add(hero_5)
        session.add(hero_6)
        session.add(hero_7)

        session.commit()


def update_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Boy")
        results = session.exec(statement)
        hero_1 = results.one()
        print("Hero 1:", hero_1)

        statement = select(Hero).where(Hero.name == "Captain North America")
        results = session.exec(statement)
        hero_2 = results.one()
        print("Hero 2:", hero_2)

        hero_1.age = 16
        hero_1.name = "Spider-Youngster"
        session.add(hero_1)

        hero_2.name = "Captain North America Except Canada"
        hero_2.age = 110
        session.add(hero_2)

        session.commit()
        session.refresh(hero_1)
        session.refresh(hero_2)

        print("Updated hero 1:", hero_1)
        print("Updated hero 2:", hero_2)


def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")  # (1)!
        results = session.exec(statement)  # (2)!
        hero = results.one()  # (3)!
        print("Hero: ", hero)  # (4)!

        session.delete(hero)  # (5)!
        session.commit()  # (6)!

        print("Deleted hero:", hero)  # (7)!

        statement = select(Hero).where(Hero.name == "Spider-Youngster")  # (8)!
        results = session.exec(statement)  # (9)!
        hero = results.first()  # (10)!

        if hero is None:  # (11)!
            print("There's no hero named Spider-Youngster")  # (12)!
    # (13)!


def main():
    create_db_and_tables()
    create_heroes()
    update_heroes()
    delete_heroes()


if __name__ == "__main__":
    main()

Wählen Sie den Helden aus, den wir löschen werden.

Führen Sie die Abfrage mit dem Select-Statement-Objekt aus.

Dies erzeugt die Ausgabe

INFO Engine BEGIN (implicit)
INFO Engine SELECT hero.id, hero.name, hero.secret_name, hero.age
FROM hero
WHERE hero.name = ?
INFO Engine [no key 0.00011s] ('Spider-Youngster',)

Holen Sie sich ein Heldenobjekt, wobei genau eines erwartet wird.

Tipp

Dies stellt sicher, dass nicht mehr als eines vorhanden ist und dass es genau eines ist, kein None.

Dies würde niemals None zurückgeben, stattdessen würde es eine Ausnahme auslösen.

Geben Sie das Heldenobjekt aus.

Dies erzeugt die Ausgabe

Hero:  name='Spider-Youngster' secret_name='Pedro Parqueador' age=16 id=2

Löschen Sie den Helden aus der Session.

Dies markiert den Helden als aus der Session gelöscht, aber er wird erst aus der Datenbank entfernt, wenn wir die Änderungen committen.
Committen Sie die Session.

Dies speichert die Änderungen in der Session, einschließlich des Löschens dieser Zeile.

Es erzeugt die Ausgabe
```
INFO Engine DELETE FROM hero WHERE hero.id = ?
INFO Engine [generated in 0.00020s] (2,)
INFO Engine COMMIT
```
Geben Sie das gelöschte Heldenobjekt aus.

Der Held ist in der Datenbank gelöscht. Und ist in der Session als gelöscht markiert.

Aber wir haben das Objekt immer noch im Speicher mit seinen Daten, so dass wir es verwenden können, um es auszugeben.

Dies erzeugt die Ausgabe
```
Deleted hero: name='Spider-Youngster' secret_name='Pedro Parqueador' age=16 id=2
```
Wählen Sie denselben Helden erneut aus.

Wir werden dies tun, um zu bestätigen, ob der Held wirklich gelöscht wurde.

Führen Sie die Select-Anweisung aus.

Dies erzeugt die Ausgabe

INFO Engine BEGIN (implicit)
INFO Engine SELECT hero.id, hero.name, hero.secret_name, hero.age
FROM hero
WHERE hero.name = ?
INFO Engine [no key 0.00013s] ('Spider-Youngster',)

Holen Sie sich das "erste" Element aus results.

Wenn keine Elemente gefunden wurden, gibt dies None zurück, was wir erwarten.
Überprüfen Sie, ob das erste Element aus den Ergebnissen None ist.
Wenn dieses erste Element tatsächlich None ist, bedeutet dies, dass es korrekt aus der Datenbank gelöscht wurde.

Nun können wir eine Nachricht ausgeben, um dies zu bestätigen.

Dies erzeugt die Ausgabe
```
There's no hero named Spider-Youngster
```
Dies ist das Ende des with-Blocks, hier führt die Session ihren Schließungscode aus.

Dies erzeugt die Ausgabe
```
INFO Engine ROLLBACK
```

from typing import Optional

from sqlmodel import Field, Session, SQLModel, create_engine, select


class Hero(SQLModel, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    secret_name: str
    age: Optional[int] = Field(default=None, index=True)


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

engine = create_engine(sqlite_url, echo=True)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


def create_heroes():
    hero_1 = Hero(name="Deadpond", secret_name="Dive Wilson")
    hero_2 = Hero(name="Spider-Boy", secret_name="Pedro Parqueador")
    hero_3 = Hero(name="Rusty-Man", secret_name="Tommy Sharp", age=48)
    hero_4 = Hero(name="Tarantula", secret_name="Natalia Roman-on", age=32)
    hero_5 = Hero(name="Black Lion", secret_name="Trevor Challa", age=35)
    hero_6 = Hero(name="Dr. Weird", secret_name="Steve Weird", age=36)
    hero_7 = Hero(name="Captain North America", secret_name="Esteban Rogelios", age=93)

    with Session(engine) as session:
        session.add(hero_1)
        session.add(hero_2)
        session.add(hero_3)
        session.add(hero_4)
        session.add(hero_5)
        session.add(hero_6)
        session.add(hero_7)

        session.commit()


def update_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Boy")
        results = session.exec(statement)
        hero_1 = results.one()
        print("Hero 1:", hero_1)

        statement = select(Hero).where(Hero.name == "Captain North America")
        results = session.exec(statement)
        hero_2 = results.one()
        print("Hero 2:", hero_2)

        hero_1.age = 16
        hero_1.name = "Spider-Youngster"
        session.add(hero_1)

        hero_2.name = "Captain North America Except Canada"
        hero_2.age = 110
        session.add(hero_2)

        session.commit()
        session.refresh(hero_1)
        session.refresh(hero_2)

        print("Updated hero 1:", hero_1)
        print("Updated hero 2:", hero_2)


def delete_heroes():
    with Session(engine) as session:
        statement = select(Hero).where(Hero.name == "Spider-Youngster")  # (1)!
        results = session.exec(statement)  # (2)!
        hero = results.one()  # (3)!
        print("Hero: ", hero)  # (4)!

        session.delete(hero)  # (5)!
        session.commit()  # (6)!

        print("Deleted hero:", hero)  # (7)!

        statement = select(Hero).where(Hero.name == "Spider-Youngster")  # (8)!
        results = session.exec(statement)  # (9)!
        hero = results.first()  # (10)!

        if hero is None:  # (11)!
            print("There's no hero named Spider-Youngster")  # (12)!
    # (13)!


def main():
    create_db_and_tables()
    create_heroes()
    update_heroes()
    delete_heroes()


if __name__ == "__main__":
    main()

Wählen Sie den Helden aus, den wir löschen werden.

Führen Sie die Abfrage mit dem Select-Statement-Objekt aus.

Dies erzeugt die Ausgabe

INFO Engine BEGIN (implicit)
INFO Engine SELECT hero.id, hero.name, hero.secret_name, hero.age
FROM hero
WHERE hero.name = ?
INFO Engine [no key 0.00011s] ('Spider-Youngster',)

Holen Sie sich ein Heldenobjekt, wobei genau eines erwartet wird.

Tipp

Dies stellt sicher, dass nicht mehr als eines vorhanden ist und dass es genau eines ist, kein None.

Dies würde niemals None zurückgeben, stattdessen würde es eine Ausnahme auslösen.

Geben Sie das Heldenobjekt aus.

Dies erzeugt die Ausgabe

Hero:  name='Spider-Youngster' secret_name='Pedro Parqueador' age=16 id=2

Löschen Sie den Helden aus der Session.

Dies markiert den Helden als aus der Session gelöscht, aber er wird erst aus der Datenbank entfernt, wenn wir die Änderungen committen.
Committen Sie die Session.

Dies speichert die Änderungen in der Session, einschließlich des Löschens dieser Zeile.

Es erzeugt die Ausgabe
```
INFO Engine DELETE FROM hero WHERE hero.id = ?
INFO Engine [generated in 0.00020s] (2,)
INFO Engine COMMIT
```
Geben Sie das gelöschte Heldenobjekt aus.

Der Held ist in der Datenbank gelöscht. Und ist in der Session als gelöscht markiert.

Aber wir haben das Objekt immer noch im Speicher mit seinen Daten, so dass wir es verwenden können, um es auszugeben.

Dies erzeugt die Ausgabe
```
Deleted hero: name='Spider-Youngster' secret_name='Pedro Parqueador' age=16 id=2
```
Wählen Sie denselben Helden erneut aus.

Wir werden dies tun, um zu bestätigen, ob der Held wirklich gelöscht wurde.

Führen Sie die Select-Anweisung aus.

Dies erzeugt die Ausgabe

INFO Engine BEGIN (implicit)
INFO Engine SELECT hero.id, hero.name, hero.secret_name, hero.age
FROM hero
WHERE hero.name = ?
INFO Engine [no key 0.00013s] ('Spider-Youngster',)

Holen Sie sich das "erste" Element aus results.

Wenn keine Elemente gefunden wurden, gibt dies None zurück, was wir erwarten.
Überprüfen Sie, ob das erste Element aus den Ergebnissen None ist.
Wenn dieses erste Element tatsächlich None ist, bedeutet dies, dass es korrekt aus der Datenbank gelöscht wurde.

Nun können wir eine Nachricht ausgeben, um dies zu bestätigen.

Dies erzeugt die Ausgabe
```
There's no hero named Spider-Youngster
```
Dies ist das Ende des with-Blocks, hier führt die Session ihren Schließungscode aus.

Dies erzeugt die Ausgabe
```
INFO Engine ROLLBACK
```

Tipp

Schauen Sie sich die Nummernblasen an, um zu sehen, was jede Codezeile tut.

Zusammenfassung¶

Um Zeilen mit SQLModel zu löschen, müssen Sie sie nur mit der Session .delete()n und dann, wie immer, die Session .commit()ten, um die Änderungen in der Datenbank zu speichern. 🔥