//// tab | لینوکس، مک‌اواس، ویندوز بش

<div class="termy">

```console
// می‌تونی یه متغیر محیطی به اسم MY_NAME بسازی با
$ export MY_NAME="Wade Wilson"

// بعد می‌تونی با برنامه‌های دیگه ازش استفاده کنی، مثل
$ echo "Hello $MY_NAME"

Hello Wade Wilson
```

</div>

////

//// tab | ویندوز پاورشل

<div class="termy">

```console

//// tab | Linux, macOS, Windows Bash

<div class="termy">

```console
// You could create an env var MY_NAME with
$ export MY_NAME="Wade Wilson"

// Then you could use it with other programs, like
$ echo "Hello $MY_NAME"

Hello Wade Wilson
```

</div>

////

//// tab | Windows PowerShell

<div class="termy">

```console

## Type annotation vs `Depends` { #type-annotation-vs-depends }

Notice how we write `CommonQueryParams` twice in the above code:

//// tab | Python 3.8+

```Python
commons: Annotated[CommonQueryParams, Depends(CommonQueryParams)]
```

////

//// tab | Python 3.8+ non-Annotated

/// tip

Prefer to use the `Annotated` version if possible.

///

```Python

This also means that in Python 3.10, you can use `Something | None`:

//// tab | Python 3.10+

```Python hl_lines="1"
{!> ../../docs_src/python_types/tutorial009_py310.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="1  4"
{!> ../../docs_src/python_types/tutorial009.py!}
```

////

//// tab | Python 3.8+ alternative

```Python hl_lines="1  4"

                final long lm = f.lastModified();

                if (lm > lastModified) {
                    lastModified = lm;
                    TAB.clear();
                    alt = 0;
                    populate(new FileReader(f));
                }
                result = (NbtAddress) TAB.get(name);
            }
        } catch (final FileNotFoundException fnfe) {
            if (LogStream.level > 1) {

یعنی توی پایتون 3.10، می‌تونی از `Something | None` استفاده کنی:

//// tab | Python 3.10+

```Python hl_lines="1"
{!> ../../docs_src/python_types/tutorial009_py310.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="1  4"
{!> ../../docs_src/python_types/tutorial009.py!}
```

////

//// tab | Python 3.8+ جایگزین

```Python hl_lines="1  4"

///

//// tab | Linux, macOS

<div class="termy">

```console
$ source .venv/bin/activate
```

</div>

////

//// tab | Windows PowerShell

<div class="termy">

```console
$ .venv\Scripts\Activate.ps1
```

</div>

////

//// tab | Windows Bash

We had this type annotation:

//// tab | Python 3.10+

```Python
q: str | None = None
```

////

//// tab | Python 3.8+

```Python
q: Union[str, None] = None
```

////

What we will do is wrap that with `Annotated`, so it becomes:

//// tab | Python 3.10+

```Python
q: Annotated[str | None] = None
```

////

//// tab | Python 3.8+

```Python

Both *path operations* require an `X-Token` header.

//// tab | Python 3.10+

```Python
{!> ../../docs_src/app_testing/app_b_an_py310/main.py!}
```

////

//// tab | Python 3.9+

```Python
{!> ../../docs_src/app_testing/app_b_an_py39/main.py!}
```

////

//// tab | Python 3.8+

```Python
{!> ../../docs_src/app_testing/app_b_an/main.py!}
```

//// tab | Python 3.8+

```Python hl_lines="1"
async def needy_dependency(fresh_value: Annotated[str, Depends(get_value, use_cache=False)]):
    return {"fresh_value": fresh_value}
```

////

//// tab | Python 3.8+ non-Annotated

/// tip

Prefer to use the `Annotated` version if possible.

///