// must start and end with an alphanumeric character (e.g. 'MyName',  or 'my.name',  or
  // '123-abc', regex used for validation is '([A-Za-z0-9][-A-Za-z0-9_.]*)?[A-Za-z0-9]') with an
  // optional DNS subdomain prefix and '/' (e.g. 'example.com/MyName')
  //
  // Required.
  optional string name = 1;

  // Expression represents the expression which will be evaluated by CEL. Must evaluate to bool.

```

</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")
print(f"Hello {name} from Python")
```

/// tip

For example, in the URL:

```
http://127.0.0.1:8000/items/?skip=0&limit=10
```

...the query parameters are:

* `skip`: with a value of `0`
* `limit`: with a value of `10`

As they are part of the URL, they are "naturally" strings.

But when you declare them with Python types (in the example above, as `int`), they are converted to that type and validated against it.

import okhttp3.Headers.Companion.headersOf
import okhttp3.HttpUrl.Companion.toHttpUrl
import okhttp3.RequestBody.Companion.toRequestBody

class RequestCommonTest {
  @Test
  fun constructorNormal() {
    val url = "https://example.com/".toHttpUrl()
    val body = "hello".toRequestBody()
    val headers = headersOf("User-Agent", "RequestTest")
    val method = "PUT"
    val request =
      Request(
        url = url,
        headers = headers,

```Python hl_lines="6-7"
{!../../docs_src/path_params/tutorial001.py!}
```

La valeur du paramètre `item_id` sera transmise à la fonction dans l'argument `item_id`.

Donc, si vous exécutez cet exemple et allez sur <a href="http://127.0.0.1:8000/items/foo" class="external-link" target="_blank">http://127.0.0.1:8000/items/foo</a>,
vous verrez comme réponse :

```JSON
{"item_id":"foo"}
```

  <modelVersion>4.0.0</modelVersion>
  <groupId>com.example.group</groupId>
  <artifactId>testvalidpom</artifactId>
  <version>0.0.1-SNAPSHOT</version>

  <description>
    This will test if the module validator recognized that this dependency with classifier
    is not the same as the module itself.
  </description>
  <dependencies>
    <dependency>
      <groupId>com.example.group</groupId>
      <artifactId>testvalidpom</artifactId>

  <modelVersion>4.0.0</modelVersion>
  <groupId>com.example.group</groupId>
  <artifactId>testinvalidpom</artifactId>
  <version>0.0.1-SNAPSHOT</version>

  <description>
    This will test if the module validator recognized that this
    dependency is the same as the module itself.
  </description>
  <dependencies>
    <dependency>
      <groupId>com.example.group</groupId>
      <artifactId>testinvalidpom</artifactId>

    "output": "ab--c.xn--zca"
  },
  {
    "input": "ab--c.ß",
    "output": "ab--c.xn--zca"
  },
  {
    "comment": "CheckJoiners is true",
    "input": "\u200D.example",
    "output": null
  },
  {
    "input": "xn--1ug.example",
    "output": null
  },
  {
    "comment": "CheckBidi is true",
    "input": "يa",
    "output": null
  },
  {
    "input": "xn--a-yoc",
    "output": null

It would also mean that if you get data from the `Request` object directly (for example, read the body) it won't be validated, converted or documented (with OpenAPI, for the automatic API user interface) by FastAPI.

Although any other parameter declared normally (for example, the body with a Pydantic model) would still be validated, converted, annotated, etc.

Make sure you create a [virtual environment](../virtual-environments.md){.internal-link target=_blank}, activate it, and then install it, for example:

```console
$ pip install python-multipart
```

///

/// note

This is supported since FastAPI version `0.113.0`. 🤓

///

## Pydantic Models for Forms