### Virtual environment with `venv`

You can create an isolated virtual local environment in a directory using Python's `venv` module. Let's do this in the cloned repository (where the `requirements.txt` is):

<div class="termy">

```console
$ python -m venv env
```

</div>

Bu insanlar:

* [GitHub-da başqalarının suallarına kömək edirlər](help-fastapi.md#help-others-with-questions-in-github){.internal-link target=_blank}.
* [Pull Request-lər yaradırlar](help-fastapi.md#create-a-pull-request){.internal-link target=_blank}.
* Pull Request-ləri ([xüsusilə tərcümələr üçün vacib olan](contributing.md#translations){.internal-link target=_blank}.) nəzərdən keçirirlər.

Bu insanlara təşəkkür edirəm. 👏 🙇

    To use `TestClient`, first install <a href="https://www.python-httpx.org" class="external-link" target="_blank">`httpx`</a>.

    E.g. `pip install httpx`.

Import `TestClient`.

Create a `TestClient` by passing your **FastAPI** application to it.

Create functions with a name that starts with `test_` (this is standard `pytest` conventions).

Use the `TestClient` object the same way as you do with `httpx`.

Bu insanlar:

* [GitHubdaki soruları cevaplayarak diğerlerine yardım ediyor](help-fastapi.md#help-others-with-questions-in-github){.internal-link target=_blank}.
* [Pull Request'ler oluşturuyor](help-fastapi.md#create-a-pull-request){.internal-link target=_blank}.
* Pull Request'leri gözden geçiriyorlar, [özellikle çeviriler için bu çok önemli](contributing.md#translations){.internal-link target=_blank}.

Onları bir alkışlayalım. 👏 🙇

You can create production applications with **FastAPI** right now (and you have probably been doing it for some time), you just have to make sure that you use a version that works correctly with the rest of your code.

## Pin your `fastapi` version

                                    }
                                }
                            },
                        },
                    },
                    "summary": "Create Item",
                    "operationId": "create_item_items__post",
                    "requestBody": {
                        "content": {
                            "application/json": {

                                    }
                                }
                            },
                        },
                    },
                    "summary": "Create Item",
                    "operationId": "create_item_items__post",
                    "requestBody": {
                        "content": {
                            "application/json": {

    ```

`Field` works the same way as `Query`, `Path` and `Body`, it has all the same parameters, etc.

!!! note "Technical Details"
    Actually, `Query`, `Path` and others you'll see next create objects of subclasses of a common `Param` class, which is itself a subclass of Pydantic's `FieldInfo` class.

    And Pydantic's `Field` returns an instance of `FieldInfo` as well.

It was created to generate the HTML in the backend, not to create APIs used by a modern frontend (like React, Vue.js and Angular) or by other systems (like <abbr title="Internet of Things">IoT</abbr> devices) communicating with it.

* Running on startup
* Restarts
* Replication (the number of processes running)
* Memory
* Previous steps before starting