items = relationship("Item", back_populates="owner")


class Item(Base):
    __tablename__ = "items"

    id = Column(Integer, primary_key=True)
    title = Column(String, index=True)
    description = Column(String, index=True)
    owner_id = Column(Integer, ForeignKey("users.id"))

Each section gradually builds on the previous ones, but it's structured to separate topics, so that you can go directly to any specific one to solve your specific API needs.

It is also built to work as a future reference.

So you can come back and see exactly what you need.

## Run the code

All the code blocks can be copied and used directly (they are actually tested Python files).

```

!!! tip
    The *path operation* for `swagger_ui_redirect` is a helper for when you use OAuth2.

    If you integrate your API with an OAuth2 provider, you will be able to authenticate and come back to the API docs with the acquired credentials. And interact with it using the real OAuth2 authentication.

    Swagger UI will handle it behind the scenes for you, but it needs this "redirect" helper.

    items = relationship("Item", back_populates="owner")


class Item(Base):
    __tablename__ = "items"

    id = Column(Integer, primary_key=True)
    title = Column(String, index=True)
    description = Column(String, index=True)
    owner_id = Column(Integer, ForeignKey("users.id"))

    items = relationship("Item", back_populates="owner")


class Item(Base):
    __tablename__ = "items"

    id = Column(Integer, primary_key=True)
    title = Column(String, index=True)
    description = Column(String, index=True)
    owner_id = Column(Integer, ForeignKey("users.id"))

So, during that time, the computer can go and do some other work, while "slow-file" 📝 finishes.

Then the computer / program 🤖 will come back every time it has a chance because it's waiting again, or whenever it 🤖 finished all the work it had at that point. And it 🤖 will see if any of the tasks it was waiting for have already finished, doing whatever it had to do.

    invoice.

    And this path operation will:

    * Send the invoice to the client.
    * Collect the money from the client.
    * Send a notification back to the API user (the external developer), as a callback.
        * At this point is that the API will somehow send a POST request to the
            external API with the notification of the invoice event

    * `UUID` objects.
    * Database models.
    * ...and many more.
* Automatic interactive API documentation, including 2 alternative user interfaces:
    * Swagger UI.
    * ReDoc.

---

Coming back to the previous code example, **FastAPI** will:

* Validate that there is an `item_id` in the path for `GET` and `PUT` requests.
* Validate that the `item_id` is of type `int` for `GET` and `PUT` requests.

I (the author, [@tiangolo](https://twitter.com/tiangolo)) will review it thoroughly and get back to you.

## Public Discussions

Please restrain from publicly discussing a potential security vulnerability. 🙊

Whenever you pass exactly the same content (exactly the same password) you get exactly the same gibberish.

But you cannot convert from the gibberish back to the password.

##### Why use password hashing

If your database is stolen, the thief won't have your users' plaintext passwords, only the hashes.