```JSON
{"item_id":3}
```

/// check

👀 👈 💲 👆 🔢 📨 (& 📨) `3`, 🐍 `int`, 🚫 🎻 `"3"`.

, ⏮️ 👈 🆎 📄, **FastAPI** 🤝 👆 🏧 📨 <abbr title="converting the string that comes from an HTTP request into Python data">"✍"</abbr>.

///

## 💽 🔬

Because **FastAPI** doesn't make any changes to a `Response` you return, you have to make sure its contents are ready for it.

For example, you cannot put a Pydantic model in a `JSONResponse` without first converting it to a `dict` with all the data types (like `datetime`, `UUID`, etc) converted to JSON-compatible types.

For those cases, you can use the `jsonable_encoder` to convert your data before passing it to a response:

  public void testBigToDouble() {
    for (BigInteger b : ALL_BIGINTEGER_CANDIDATES) {
      if (b.doubleValue() != DoubleUtils.bigToDouble(b)) {
        failFormat(
            "Converting %s to double: expected doubleValue %s but got bigToDouble %s",
            b, b.doubleValue(), DoubleUtils.bigToDouble(b));
      }
    }
  }

  public void testEnsureNonNegative() {

* `frozenset`:
    * In requests and responses, treated the same as a `set`:
        * In requests, a list will be read, eliminating duplicates and converting it to a `set`.
        * In responses, the `set` will be converted to a `list`.
        * The generated schema will specify that the `set` values are unique (using JSON Schema's `uniqueItems`).
* `bytes`:

{"item_id":3}
```

/// check

Notice that the value your function received (and returned) is `3`, as a Python `int`, not a string `"3"`.

So, with that type declaration, **FastAPI** gives you automatic request <abbr title="converting the string that comes from an HTTP request into Python data">"parsing"</abbr>.

///

## Data validation

4️⃣. `Author` 🎻 ⚙️ `response_model` 🔢.

5️⃣. 👆 💪 ⚙️ 🎏 🐩 🆎 ✍ ⏮️ 🎻 📨 💪.

    👉 💼, ⚫️ 📇 `Item` 🎻.

6️⃣. 📥 👥 🛬 📖 👈 🔌 `items` ❔ 📇 🎻.

    FastAPI 🎯 <abbr title="converting the data to a format that can be transmitted">✍</abbr> 💽 🎻.

7️⃣. 📥 `response_model` ⚙️ 🆎 ✍ 📇 `Author` 🎻.

    🔄, 👆 💪 🌀 `dataclasses` ⏮️ 🐩 🆎 ✍.

8️⃣. 👀 👈 👉 *➡ 🛠️ 🔢* ⚙️ 🥔 `def` ↩️ `async def`.

  public void testBigToDouble() {
    for (BigInteger b : ALL_BIGINTEGER_CANDIDATES) {
      if (b.doubleValue() != DoubleUtils.bigToDouble(b)) {
        failFormat(
            "Converting %s to double: expected doubleValue %s but got bigToDouble %s",
            b, b.doubleValue(), DoubleUtils.bigToDouble(b));
      }
    }
  }

  public void testEnsureNonNegative() {

    val cookie = cookies[0]
    assertThat(cookie.name).isEqualTo("a")
    assertThat(cookie.value).isEqualTo("android")
    assertThat(cookie.commentURL).isNull()
    assertThat(cookie.discard).isFalse()
    // Converting to a fixed date can cause rounding!
    assertThat(cookie.maxAge.toDouble()).isCloseTo(60.0, 5.0)
    assertThat(cookie.path).isEqualTo("/path")
    assertThat(cookie.secure).isTrue()
  }

  @Test

269D          ; valid                  ;      ; NV8    # 5.1  OUTLINED WHITE STAR
269E..269F    ; valid                  ;      ; NV8    # 5.2  THREE LINES CONVERGING RIGHT..THREE LINES CONVERGING LEFT
26A0..26A1    ; valid                  ;      ; NV8    # 4.0  WARNING SIGN..HIGH VOLTAGE SIGN
26A2..26B1    ; valid                  ;      ; NV8    # 4.1  DOUBLED FEMALE SIGN..FUNERAL URN

Taking data from:

* The path as parameters.
* Headers.
* Cookies.
* etc.

And by doing so, **FastAPI** is validating that data, converting it and generating documentation for your API automatically.

But there are situations where you might need to access the `Request` object directly.

## Details about the `Request` object