}

        // Fill the receive buffer without holding any locks.
        val read = source.read(receiveBuffer, remainingByteCount)
        if (read == -1L) throw EOFException()
        remainingByteCount -= read

        // Move the received data to the read buffer to the reader can read it. If this source has
        // been closed since this read began we must discard the incoming data and tell the
        // connection we've done so.

* Read what I write (or follow me) on <a href="https://dev.to/tiangolo" class="external-link" target="_blank">**Dev.to**</a> or <a href="https://medium.com/@tiangolo" class="external-link" target="_blank">**Medium**</a>.
    * Read other ideas, articles, and read about tools I have created.
    * Follow me to read when I publish something new.

## Tweet about **FastAPI**

# Static Files - `StaticFiles`

You can use the `StaticFiles` class to serve static files, like JavaScript, CSS, images, etc.

Read more about it in the [FastAPI docs for Static Files](https://fastapi.tiangolo.com/tutorial/static-files/).

You can import it directly from `fastapi.staticfiles`:

```python
from fastapi.staticfiles import StaticFiles
```

    // Use it with other programs, like
    $ echo "Hello $Env:MY_NAME"

    Hello Wade Wilson
    ```

    </div>

### Read env vars in Python

You could also create environment variables outside of Python, in the terminal (or with any other method), and then read them in Python.

For example you could have a file `main.py` with:

```Python hl_lines="3"
import os

name = os.getenv("MY_NAME", "World")

# Test Client - `TestClient`

You can use the `TestClient` class to test FastAPI applications without creating an actual HTTP and socket connection, just communicating directly with the FastAPI code.

Read more about it in the [FastAPI docs for Testing](https://fastapi.tiangolo.com/tutorial/testing/).

You can import it directly from `fastapi.testclient`:

```python
from fastapi.testclient import TestClient
```

* Assign that result to the parameter in your *path operation function*.

```mermaid
graph TB

common_parameters(["common_parameters"])
read_items["/items/"]
read_users["/users/"]

common_parameters --> read_items
common_parameters --> read_users
```

This way you write shared code once and **FastAPI** takes care of calling it for your *path operations*.

!!! check

* Create a file `main.py` with:

```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">
<summary>Or use <code>async def</code>...</summary>

Takes some data and returns an `application/json` encoded response.

This is the default response used in **FastAPI**, as you read above.

### `ORJSONResponse`

A fast alternative JSON response using <a href="https://github.com/ijl/orjson" class="external-link" target="_blank">`orjson`</a>, as you read above.

### `UJSONResponse`

    a.setString(0, "a1")
    assertThat(cache.remove("a")).isTrue()
    a.setString(1, "a2")
    a.commit()
    assertAbsent("a")
  }

  /**
   * Each read sees a snapshot of the file at the time read was called. This means that two reads of
   * the same key can see different data.
   */
  @ParameterizedTest
  @ArgumentsSource(FileSystemParamProvider::class)

* Crie um arquivo `main.py` com:

```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">
<summary>Ou use <code>async def</code>...</summary>