// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package main

import (
	"bytes"
	"crypto/md5"
	"encoding/base64"
	"encoding/binary"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"log"
	"os"
	"path/filepath"
	"regexp"
	"sort"

Sebastián Ramírez <******@****.***> 1730366006 +0100

Poorna <******@****.***> 1727214611 -0700

<div class="termy">

```console
// Here we don't set the env var yet
$ python main.py

// As we didn't set the env var, we get the default value

Hello World from Python

// But if we create an environment variable first
$ export MY_NAME="Wade Wilson"

// And then call the program again
$ python main.py

// Now it can read the environment variable

Hello Wade Wilson from Python
```

DIR:
  DIR points to a directory on a filesystem. When you want to combine
  multiple drives into a single large system, pass one directory per
  filesystem separated by space. You may also use a '...' convention
  to abbreviate the directory arguments. Remote directories in a
  distributed setup are encoded as HTTP(s) URIs.
{{if .VisibleFlags}}
FLAGS:
  {{range .VisibleFlags}}{{.}}
  {{end}}{{end}}

### The main app file

Now we create a dependency that returns a new `config.Settings()`.

//// tab | Python 3.9+

```Python hl_lines="6  12-13"
{!> ../../docs_src/settings/app02_an_py39/main.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="6  12-13"
{!> ../../docs_src/settings/app02_an/main.py!}
```

////

One particular advantage that is not necessarily obvious is that you can **generate clients** (sometimes called <abbr title="Software Development Kits">**SDKs**</abbr> ) for your API, for many different **programming languages**.

## OpenAPI Client Generators

There are many tools to generate clients from **OpenAPI**.

///

## The main `FastAPI`

Now, let's see the module at `app/main.py`.

Here's where you import and use the class `FastAPI`.

This will be the main file in your application that ties everything together.

And as most of your logic will now live in its own specific module, the main file will be quite simple.

### Import `FastAPI`

* [fess_label_en.properties](https://github.com/codelibs/fess/blob/master/src/main/resources/fess_label_en.properties)
* [fess_message_en.properties](https://github.com/codelibs/fess/blob/master/src/main/resources/fess_message_en.properties)

/// note | "Technische Details"

In der OpenAPI-Spezifikation wird das <a href="https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.0.3.md#operation-object" class="external-link" target="_blank">Operationsobjekt</a> genannt.

///

Es hat alle Informationen zur *Pfadoperation* und wird zur Erstellung der automatischen Dokumentation verwendet.