```

</div>

////

This information will be useful when learning about [Virtual Environments](virtual-environments.md){.internal-link target=_blank}.

## Conclusion { #conclusion }

With this you should have a basic understanding of what **environment variables** are and how to use them in Python.

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I think `Union[SomeType, None]` is more explicit about what it means.

It's just about the words and names. But those words can affect how you and your teammates think about the code.

As an example, let's take this function:

{* ../../docs_src/python_types/tutorial009c.py hl[1,4] *}

/// note

Some response codes (see the next section) indicate that the response does not have a body.

FastAPI knows this, and will produce OpenAPI docs that state there is no response body.

///

## About HTTP status codes { #about-http-status-codes }

/// note

If you already know what HTTP status codes are, skip to the next section.

///

In HTTP, you send a numeric status code of 3 digits as part of the response.

  }

  private void doTestCollapseWithNoChange(String inout) {
    assertSame(inout, is('-').collapseFrom(inout, '_'));
    assertSame(inout, is('-').or(is('#')).collapseFrom(inout, '_'));
    assertSame(inout, isNot('x').collapseFrom(inout, '_'));
    assertSame(inout, is('x').negate().collapseFrom(inout, '_'));
    assertSame(inout, anyOf("-").collapseFrom(inout, '_'));
    assertSame(inout, anyOf("-#").collapseFrom(inout, '_'));

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

## Details about the `Request` object { #details-about-the-request-object }

///

/// tip

To declare form bodies, you need to use `Form` explicitly, because without it the parameters would be interpreted as query parameters or body (JSON) parameters.

///

## About "Form Fields" { #about-form-fields }

The way HTML forms (`<form></form>`) sends the data to the server normally uses a "special" encoding for that data, it's different from JSON.

I'll show you some concrete examples in the next chapters.

---

Then the next concepts to consider are all about the program running your actual API (e.g. Uvicorn).

## Program and Process { #program-and-process }

We will talk a lot about the running "**process**", so it's useful to have clarity about what it means, and what's the difference with the word "**program**".

### What is a Program { #what-is-a-program }

	err := buildServerCtxt(ctxt, &globalServerCtxt)
	if err != nil {
		log.Fatalln(err)
	}
	handleCommonArgs(globalServerCtxt)
	pools, _, err := createServerEndpoints(globalMinioAddr, globalServerCtxt.Layout.pools, globalServerCtxt.Layout.legacy)
	if err != nil {
		log.Fatalln(err)
	}

	zipFile, err := os.Create("format.json.zip")
	if err != nil {
		log.Fatalf("failed to create format.json.zip: %v", err)
	}
	defer zipFile.Close()

     */
    InputStream getInputStream() throws IOException;

    /**
     * Provides a user-friendly hint about the location of the source. This could be a local file path, a URI or just an
     * empty string. The intention is to assist users during error reporting.
     *
     * @return A user-friendly hint about the location of the source, never {@code null}.
     */
    String getLocation();