```

</div>


让我们看看每个选项的含义：

* `main:app`：这与 Uvicorn 使用的语法相同，`main` 表示名为"`main`"的 Python 模块，因此是文件 `main.py`。 `app` 是 **FastAPI** 应用程序的变量名称。
     * 你可以想象 `main:app` 相当于一个 Python `import` 语句，例如：

        ```Python
        from main import app
        ```

     * 因此，`main:app` 中的冒号相当于 `from main import app` 中的 Python `import` 部分。

* `--workers`：要使用的worker进程数量，每个进程将运行一个 Uvicorn worker进程，在本例中为 4 个worker进程。

/* Test Code */
#include <sdtio.h>


int main(void)
{
    printf("テスト");

        - docs/en/docs/**
        - docs_src/**
      - all-globs-to-all-files:
        - '!fastapi/**'
        - '!pyproject.toml'
        - '!docs/en/data/sponsors.yml'
        - '!docs/en/overrides/main.html'

lang-all:
  - all:
    - changed-files:
      - any-glob-to-any-file:
        - docs/*/docs/**
      - all-globs-to-all-files:
        - '!docs/en/docs/**'
        - '!fastapi/**'

FROM python:3.9

RUN pip install httpx PyGithub "pydantic==1.5.1" "pyyaml>=5.3.1,<6.0.0"

COPY ./app /app

```console
$ <pre> <font color="#4E9A06">fastapi</font> run --workers 4 <u style="text-decoration-style:single">main.py</u>
<font color="#3465A4">INFO    </font> Using path <font color="#3465A4">main.py</font>
<font color="#3465A4">INFO    </font> Resolved absolute path <font color="#75507B">/home/user/code/awesomeapp/</font><font color="#AD7FA8">main.py</font>

<span style="color: green;">INFO</span>:     Application startup complete.
```

</div>

/// note

`uvicorn main:app` 命令含义如下:

* `main`：`main.py` 文件（一个 Python「模块」）。
* `app`：在 `main.py` 文件中通过 `app = FastAPI()` 创建的对象。
* `--reload`：让服务器在更新代码后重新启动。仅在开发时使用该选项。

///

在输出中，会有一行信息像下面这样：

```hl_lines="4"
INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)

// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package main

import (
	"bytes"
	"context"
	"crypto/tls"
	"encoding/json"
	"flag"
	"fmt"
	"log"
	"net/http"
	"net/url"
	"strings"

	minio "github.com/minio/minio-go/v7"

// be obtained by following the instructions at
// https://github.com/libimobiledevice/libimobiledevice.
package main

import (
	"bytes"
	"crypto/x509"
	"fmt"
	"os"
	"os/exec"
	"strings"
)

func main() {
	udids := getLines(exec.Command("idevice_id", "-l"))
	if len(udids) == 0 {
		fail("no udid found; is a device connected?")
	}

<span style="color: green;">INFO</span>:     Application startup complete.
```

</div>

/// note

Câu lệnh `uvicorn main:app` được giải thích như sau:

* `main`: tệp tin `main.py` (một Python "mô đun").
* `app`: một object được tạo ra bên trong `main.py` với dòng `app = FastAPI()`.
* `--reload`: làm server khởi động lại sau mỗi lần thay đổi. Chỉ sử dụng trong môi trường phát triển.

///

Trong output, có một dòng giống như:

from fastapi import FastAPI
from fastapi.responses import PlainTextResponse

app = FastAPI()


@app.get("/", response_class=PlainTextResponse)
async def main():