/// tip

To understand environment variables you can read [Environment Variables](../environment-variables.md){.internal-link target=_blank}.

///

## Types and validation

These environment variables can only handle text strings, as they are external to Python and have to be compatible with other programs and the rest of the system (and even with different operating systems, as Linux, Windows, macOS).

{* ../../docs_src/first_steps/tutorial001.py *}

Copy that to a file `main.py`.

Run the live server:

<div class="termy">

```console
$ <font color="#4E9A06">fastapi</font> dev <u style="text-decoration-style:single">main.py</u>
<font color="#3465A4">INFO    </font> Using path <font color="#3465A4">main.py</font>

	golang.org/x/crypto v0.28.0 // indirect
	golang.org/x/exp v0.0.0-20240719175910-8a7402abbf56 // indirect
	golang.org/x/mod v0.20.0 // indirect
	golang.org/x/term v0.25.0 // indirect
	golang.org/x/text v0.19.0 // indirect
	golang.org/x/tools v0.24.0 // indirect
	gopkg.in/evanphx/json-patch.v4 v4.12.0 // indirect
	gopkg.in/inf.v0 v0.9.1 // indirect
	gopkg.in/ini.v1 v1.67.0 // indirect

labels.facet_filetype_pdf	=	PDF
labels.facet_filetype_fb2	=	FictionBook
labels.facet_filetype_epub	=	EPUB
labels.facet_filetype_ibooks	=	iBooks
labels.facet_filetype_txt	=	Plain Text
labels.facet_filetype_rtf	=	Rich Text Format
labels.facet_filetype_chm	=	Compiled HTML Help
labels.facet_filetype_zip	=	ZIP Archive
labels.facet_filetype_7z	=	7z Archive
labels.facet_filetype_bz	=	Bz Archive

* In code blocks within the Markdown document, translate comments (`# a comment`), but leave the rest unchanged.

* Do not change anything enclosed in "``" (inline code).

* In lines starting with `///` translate only the ` "... Text ..."` part. Leave the rest unchanged.

* You can translate info boxes like `/// warning` with for example `/// warning | Achtung`. But do not change the word immediately after the `///`, it determines the color of the info box.

			continue
		}

		// In accordance with https://docs.aws.amazon.com/AmazonS3/latest/API/RESTObjectPOST.html
		// The file or text content.
		// The file or text content must be the last field in the form.
		// You cannot upload more than one file at a time.
		reader = part

		possibleShardSize := (r.ContentLength - headerLen)

  /**
   * Returns a string containing the supplied unsigned {@code int} values separated by {@code
   * separator}. For example, {@code join("-", 1, 2, 3)} returns the string {@code "1-2-3"}.
   *
   * @param separator the text that should appear between consecutive values in the resulting string
   *     (but not at the start or end)
   * @param array an array of unsigned {@code int} values, possibly empty
   */

  /**
   * Returns a string containing the supplied unsigned {@code int} values separated by {@code
   * separator}. For example, {@code join("-", 1, 2, 3)} returns the string {@code "1-2-3"}.
   *
   * @param separator the text that should appear between consecutive values in the resulting string
   *     (but not at the start or end)
   * @param array an array of unsigned {@code int} values, possibly empty
   */

import assertk.assertions.isNull
import assertk.assertions.isTrue
import java.math.BigInteger
import java.security.KeyFactory
import java.security.spec.PKCS8EncodedKeySpec
import java.security.spec.X509EncodedKeySpec
import java.text.SimpleDateFormat
import java.util.Date
import java.util.TimeZone
import okhttp3.tls.HeldCertificate
import okhttp3.tls.decodeCertificatePem
import okhttp3.tls.internal.der.ObjectIdentifiers.BASIC_CONSTRAINTS

// Copyright 2017 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

TEXT errors(SB),$0
	MOVW	(F0), R1           // ERROR "illegal base register"
	MOVB	(F0), R1           // ERROR "illegal base register"
	MOVH	(F0), R1           // ERROR "illegal base register"
	MOVF	(F0), F1           // ERROR "illegal base register"
	MOVD	(F0), F1           // ERROR "illegal base register"