/// tip

The next sections are **not necessarily "advanced"**.

And it's possible that for your use case, the solution is in one of them.

///

## Read the Tutorial first { #read-the-tutorial-first }

You could still use most of the features in **FastAPI** with the knowledge from the main [Tutorial - User Guide](../tutorial/index.md).

```console
$ fastapi dev main.py
```

But you would have to remember to pass the correct path every time you call the `fastapi` command.

Additionally, other tools might not be able to find it, for example the [VS Code Extension](../editor-support.md) or [FastAPI Cloud](https://fastapicloud.com), so it is recommended to use the `entrypoint` in `pyproject.toml`.

   *
   * @deprecated Use {@link StandardCharsets#US_ASCII} instead.
   */
  @Deprecated @J2ktIncompatible @GwtIncompatible // Charset not supported by GWT
  public static final Charset US_ASCII = StandardCharsets.US_ASCII;

  /**
   * ISO-8859-1: ISO Latin Alphabet Number 1 (ISO-LATIN-1).
   *
   * @deprecated Use {@link StandardCharsets#ISO_8859_1} instead.
   */

   *
   * @deprecated Use {@link StandardCharsets#US_ASCII} instead.
   */
  @Deprecated @J2ktIncompatible @GwtIncompatible // Charset not supported by GWT
  public static final Charset US_ASCII = StandardCharsets.US_ASCII;

  /**
   * ISO-8859-1: ISO Latin Alphabet Number 1 (ISO-LATIN-1).
   *
   * @deprecated Use {@link StandardCharsets#ISO_8859_1} instead.
   */

## Use case { #use-case }

For example, imagine that you want to return an HTTP status code of "OK" `200` by default.

But if the data didn't exist, you want to create it, and return an HTTP status code of "CREATED" `201`.

But you still want to be able to filter and convert the data you return with a `response_model`.

For those cases, you can use a `Response` parameter.

    /**
     * Reads the settings from the specified file.
     *
     * @param input The file to deserialize the settings from, must not be {@code null}.
     * @param options The options to use for deserialization, may be {@code null} to use the default values.
     * @return The deserialized settings, never {@code null}.
     * @throws IOException If the settings could not be deserialized.

    /**
     * Reads the toolchains from the specified file.
     *
     * @param input The file to deserialize the toolchains from, must not be {@code null}.
     * @param options The options to use for deserialization, may be {@code null} to use the default values.
     * @return The deserialized toolchains, never {@code null}.
     * @throws IOException If the toolchains could not be deserialized.

# or more contributor license agreements. Licensed under the Elastic License
# 2.0 and the Server Side Public License, v 1; you may not use this file except
# in compliance with, at your election, the Elastic License 2.0 or the Server
# Side Public License, v 1.

com.carrotsearch.randomizedtesting.RandomizedTest#globalTempDir() @ Use newTempDirPath() instead
com.carrotsearch.randomizedtesting.annotations.Seed @ Don't commit hardcoded seeds

/*
 * Copyright 2012-2025 CodeLibs Project and the Others.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,

///

//// tab | `venv`

To create a virtual environment, you can use the `venv` module that comes with Python.

<div class="termy">

```console
$ python -m venv .venv
```

</div>

/// details | What that command means

* `python`: use the program called `python`
* `-m`: call a module as a script, we'll tell it which module next
* `venv`: use the module called `venv` that normally comes installed with Python