!!! note "Hinweis"
    FastAPI weiß, dass der Wert von `q` nicht erforderlich ist, wegen des definierten Defaultwertes `= None`

    Das `Union` in `Union[str, None]` wird von FastAPI nicht verwendet, aber es erlaubt Ihrem Editor, Sie besser zu unterstützen und Fehler zu erkennen.

## Ohne Pydantic

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

    The `Union` in `Union[str, None]` is not used by FastAPI, but will allow your editor to give you better support and detect errors.

## Without Pydantic

  // well-known group names.
  // Required.
  optional string name = 1;
}

// LimitResponse defines how to handle requests that can not be executed right now.
// +union
message LimitResponse {
  // `type` is "Queue" or "Reject".
  // "Queue" means that requests that can not be executed upon arrival
  // are held in a queue until they can be executed or a queuing limit
  // is reached.

  // well-known group names.
  // Required.
  optional string name = 1;
}

// LimitResponse defines how to handle requests that can not be executed right now.
// +union
message LimitResponse {
  // `type` is "Queue" or "Reject".
  // "Queue" means that requests that can not be executed upon arrival
  // are held in a queue until they can be executed or a queuing limit
  // is reached.

  // well-known group names.
  // Required.
  optional string name = 1;
}

// LimitResponse defines how to handle requests that can not be executed right now.
// +union
message LimitResponse {
  // `type` is "Queue" or "Reject".
  // "Queue" means that requests that can not be executed upon arrival
  // are held in a queue until they can be executed or a queuing limit
  // is reached.

  // well-known group names.
  // Required.
  optional string name = 1;
}

// LimitResponse defines how to handle requests that can not be executed right now.
// +union
message LimitResponse {
  // `type` is "Queue" or "Reject".
  // "Queue" means that requests that can not be executed upon arrival
  // are held in a queue until they can be executed or a queuing limit
  // is reached.

from functools import lru_cache
from http.server import HTTPServer, SimpleHTTPRequestHandler
from importlib import metadata
from multiprocessing import Pool
from pathlib import Path
from typing import Any, Dict, List, Optional, Union

import mkdocs.commands.build
import mkdocs.commands.serve
import mkdocs.config
import mkdocs.utils
import typer
import yaml
from jinja2 import Template

logging.basicConfig(level=logging.INFO)

* 🚥 🔢 **⭐ 🆎** (💖 `int`, `float`, `str`, `bool`, ♒️) ⚫️ 🔜 🔬 **🔢** 🔢.
* 🚥 🔢 📣 🆎 **Pydantic 🏷**, ⚫️ 🔜 🔬 📨 **💪**.

!!! note
    FastAPI 🔜 💭 👈 💲 `q` 🚫 ✔ ↩️ 🔢 💲 `= None`.

     `Union` `Union[str, None]` 🚫 ⚙️ FastAPI, ✋️ 🔜 ✔ 👆 👨‍🎨 🤝 👆 👍 🐕‍🦺 & 🔍 ❌.

## 🍵 Pydantic

### ایجاد کنید
* فایلی به نام `main.py` با محتوای زیر ایجاد کنید:

```Python
from typing import Union

from fastapi import FastAPI

app = FastAPI()


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}
```

<details markdown="1">

  //
  // Element-level accessors
  //

  /**
   * Returns a live view of the nodes which have an incident edge in common with {@code node} in
   * this graph.
   *
   * <p>This is equal to the union of {@link #predecessors(Object)} and {@link #successors(Object)}.
   *
   * <p>If {@code node} is removed from the graph after this method is called, the {@code Set}