And also after the `response` is generated, before returning it.

For example, you could add a custom header `X-Process-Time` containing the time in seconds that it took to process the request and generate a response:

```Python hl_lines="10  12-13"
{!../../../docs_src/middleware/tutorial001.py!}
```

## Other middlewares

对于这些情况，你可以使用Python的技术，将 `dict` 与 `**dict_to_unpack` 解包：
```Python
old_dict = {
    "old key": "old value",
    "second old key": "second old value",
}
new_dict = {**old_dict, "new key": "new value"}
```

这里， new_dict 将包含来自 old_dict 的所有键值对加上新的键值对：
```python
{
    "old key": "old value",
    "second old key": "second old value",
    "new key": "new value",
}
```
您可以使用该技术在路径操作中重用一些预定义的响应，并将它们与其他自定义响应相结合。
**例如：**

    response = client.post(
        "/users", json={"email": "******@****.***", "password": "secret"}
    )
    assert response.json() == {"email": "******@****.***"}


def test_filter_second_level_model():
    response = client.get("/pets/1")
    assert response.json() == {
        "name": "Nibbler",
        "owner": {"email": "******@****.***"},
    }


def test_list_of_models():

    * Si on compare Uvicorn, il faut le comparer à d'autre applications de serveurs comme Daphne, Hypercorn, uWSGI, etc.
* **Starlette** :
    * A les seconde meilleures performances après Uvicorn. Starlette utilise en réalité Uvicorn. De ce fait, il ne peut qu’être plus "lent" qu'Uvicorn car il requiert l'exécution de plus de code.

```Python
my_user: User = User(id=3, name="John Doe", joined="2018-07-19")

second_user_data = {
    "id": 4,
    "name": "Mary",
    "joined": "2018-11-30",
}

my_second_user: User = User(**second_user_data)
```

!!! info
    `**second_user_data` means:

    Pass the keys and values of the `second_user_data` dict directly as key-value arguments, equivalent to: `User(id=4, name="Mary", joined="2018-11-30")`

```

可以像这样来使用：

```Python
my_user: User = User(id=3, name="John Doe", joined="2018-07-19")

second_user_data = {
    "id": 4,
    "name": "Mary",
    "joined": "2018-11-30",
}

my_second_user: User = User(**second_user_data)
```


!!! info
    `**second_user_data` 意思是:

    直接将`second_user_data`字典的键和值直接作为key-value参数传递，等同于：`User(id=4, name="Mary", joined="2018-11-30")`

### 编辑器支持

```

👈 💪 ⤴️ ⚙️ 💖:

```Python
my_user: User = User(id=3, name="John Doe", joined="2018-07-19")

second_user_data = {
    "id": 4,
    "name": "Mary",
    "joined": "2018-11-30",
}

my_second_user: User = User(**second_user_data)
```

!!! info
    `**second_user_data` ⛓:

    🚶‍♀️ 🔑 & 💲 `second_user_data` #️⃣ 🔗 🔑-💲 ❌, 🌓: `User(id=4, name="Mary", joined="2018-11-30")`

### 👨‍🎨 🐕‍🦺

* **`300`** and above are for "Redirection".  Responses with these status codes may or may not have a body, except for `304`, "Not Modified", which must not have one.
* **`400`** and above are for "Client error" responses. These are the second type you would probably use the most.
    * An example is `404`, for a "Not Found" response.
    * For generic errors from the client, you can just use `400`.

    ```

It declares an optional query parameter `q` as a `str`, and then it just returns it.

This is quite simple (not very useful), but will help us focus on how the sub-dependencies work.

## Second dependency, "dependable" and "dependant"

Then you can create another dependency function (a "dependable") that at the same time declares a dependency of its own (so it is a "dependant" too):

=== "Python 3.10+"

    response = client.post(
        "/form/python-list", data={"items": ["first", "second", "third"]}
    )
    assert response.status_code == 200, response.text
    assert response.json() == ["first", "second", "third"]


def test_python_set_param_as_form():
    response = client.post(
        "/form/python-set", data={"items": ["first", "second", "third"]}
    )
    assert response.status_code == 200, response.text