Create a PassLib "context". This is what will be used to hash and verify passwords.

!!! tip
    The PassLib context also has functionality to use different hashing algorithms, including deprecated old ones only to allow verifying them, etc.

    For example, you could use it to read and verify passwords generated by another system (like Django) but hash any new passwords with a different algorithm like Bcrypt.

# Python Types Intro

Python has support for optional "type hints" (also called "type annotations").

These **"type hints"** or annotations are a special syntax that allow declaring the <abbr title="for example: str, int, float, bool">type</abbr> of a variable.

By declaring types for your variables, editors and tools can give you better support.

    width: 15px;
    height: 15px;
    border-radius: 50%;
    /* A little hack to display the window buttons in one pseudo element. */
    background: #d9515d;
    -webkit-box-shadow: 25px 0 0 #f4c025, 50px 0 0 #3ec930;
            box-shadow: 25px 0 0 #f4c025, 50px 0 0 #3ec930;
}

[data-termynal]:after {
    content: 'bash';
    position: absolute;
    color: var(--color-text-subtle);
    top: 5px;
    left: 0;

* Validate **complex structures**:
    * Use of hierarchical Pydantic models, Python `typing`’s `List` and `Dict`, etc.
    * And validators allow complex data schemas to be clearly and easily defined, checked and documented as JSON Schema.
    * You can have deeply **nested JSON** objects and have them all validated and annotated.
* **Extensible**:

!!! note
    FastAPI will know that the value of `q` is not required because of the default value `= None`.

    The `Union` in `Union[str, None]` will allow your editor to give you better support and detect errors.

## Additional validation

We are going to enforce that even though `q` is optional, whenever it is provided, **its length doesn't exceed 50 characters**.

    Use the chat only for other general conversations.

### Don't use the chat for questions

Keep in mind that as chats allow more "free conversation", it's easy to ask questions that are too general and more difficult to answer, so, you might not receive answers.

* **同一程序**可以有**多个进程**同时运行。

如果您检查操作系统中的“任务管理器”或“系统监视器”（或类似工具），您将能够看到许多正在运行的进程。

例如，您可能会看到有多个进程运行同一个浏览器程序（Firefox、Chrome、Edge 等）。 他们通常每个tab运行一个进程，再加上一些其他额外的进程。

<img class="shadow" src="/img/deployment/concepts/image01.png">

---

现在我们知道了术语“进程”和“程序”之间的区别，让我们继续讨论部署。

## 启动时运行

在大多数情况下，当您创建 Web API 时，您希望它**始终运行**、不间断，以便您的客户端始终可以访问它。 这是当然的，除非您有特定原因希望它仅在某些情况下运行，但大多数时候您希望它不断运行并且**可用**。

            return with_info_plain_validator_function(cls._validate)


class BaseModelWithConfig(BaseModel):
    if PYDANTIC_V2:
        model_config = {"extra": "allow"}

    else:

        class Config:
            extra = "allow"


class Contact(BaseModelWithConfig):
    name: Optional[str] = None
    url: Optional[AnyUrl] = None
    email: Optional[EmailStr] = None

                This is much simpler (less smart) than `response_model_exclude_unset`
                and `response_model_exclude_defaults`. You probably want to use one of
                those two instead of this one, as those allow returning `None` values
                when it makes sense.

                Read more about it in the

🚥 👆 ✅ 👅 "📋 👨‍💼" ⚖️ "⚙️ 🖥" (⚖️ 🎏 🧰) 👆 🏃‍♂ ⚙️, 👆 🔜 💪 👀 📚 👈 🛠️ 🏃‍♂.

& , 🖼, 👆 🔜 🎲 👀 👈 📤 💗 🛠️ 🏃 🎏 🖥 📋 (🦎, 💄, 📐, ♒️). 👫 🛎 🏃 1️⃣ 🛠️ 📍 📑, ➕ 🎏 ➕ 🛠️.

<img class="shadow" src="/img/deployment/concepts/image01.png">

---

🔜 👈 👥 💭 🔺 🖖 ⚖ **🛠️** &amp; **📋**, ➡️ 😣 💬 🔃 🛠️.

## 🏃‍♂ 🔛 🕴