<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>18.6. base64 — RFC 3548: Base16, Base32, Base64 Data Encodings — Python v3.2.2 documentation</title>
<link rel="stylesheet" href="../_static/default.css" type="text/css" />
<link rel="stylesheet" href="../_static/pygments.css" type="text/css" />
<script type="text/javascript">
var DOCUMENTATION_OPTIONS = {
URL_ROOT: '../',
VERSION: '3.2.2',
COLLAPSE_INDEX: false,
FILE_SUFFIX: '.html',
HAS_SOURCE: true
};
</script>
<script type="text/javascript" src="../_static/jquery.js"></script>
<script type="text/javascript" src="../_static/underscore.js"></script>
<script type="text/javascript" src="../_static/doctools.js"></script>
<script type="text/javascript" src="../_static/sidebar.js"></script>
<link rel="search" type="application/opensearchdescription+xml"
title="Search within Python v3.2.2 documentation"
href="../_static/opensearch.xml"/>
<link rel="author" title="About these documents" href="../about.html" />
<link rel="copyright" title="Copyright" href="../copyright.html" />
<link rel="top" title="Python v3.2.2 documentation" href="../index.html" />
<link rel="up" title="18. Internet Data Handling" href="netdata.html" />
<link rel="next" title="18.7. binhex — Encode and decode binhex4 files" href="binhex.html" />
<link rel="prev" title="18.5. mimetypes — Map filenames to MIME types" href="mimetypes.html" />
<link rel="shortcut icon" type="image/png" href="../_static/py.png" />
</head>
<body>
<div class="related">
<h3>Navigation</h3>
<ul>
<li class="right" style="margin-right: 10px">
<a href="../genindex.html" title="General Index"
accesskey="I">index</a></li>
<li class="right" >
<a href="../py-modindex.html" title="Python Module Index"
>modules</a> |</li>
<li class="right" >
<a href="binhex.html" title="18.7. binhex — Encode and decode binhex4 files"
accesskey="N">next</a> |</li>
<li class="right" >
<a href="mimetypes.html" title="18.5. mimetypes — Map filenames to MIME types"
accesskey="P">previous</a> |</li>
<li><img src="../_static/py.png" alt=""
style="vertical-align: middle; margin-top: -1px"/></li>
<li><a href="../index.html">Python v3.2.2 documentation</a> »</li>
<li><a href="index.html" >The Python Standard Library</a> »</li>
<li><a href="netdata.html" accesskey="U">18. Internet Data Handling</a> »</li>
</ul>
</div>
<div class="document">
<div class="documentwrapper">
<div class="bodywrapper">
<div class="body">
<div class="section" id="module-base64">
<span id="base64-rfc-3548-base16-base32-base64-data-encodings"></span><h1>18.6. <a class="reference internal" href="#module-base64" title="base64: RFC 3548: Base16, Base32, Base64 Data Encodings"><tt class="xref py py-mod docutils literal"><span class="pre">base64</span></tt></a> — RFC 3548: Base16, Base32, Base64 Data Encodings<a class="headerlink" href="#module-base64" title="Permalink to this headline">¶</a></h1>
<p id="index-0">This module provides data encoding and decoding as specified in <span class="target" id="index-1"></span><a class="rfc reference external" href="http://tools.ietf.org/html/rfc3548.html"><strong>RFC 3548</strong></a>.
This standard defines the Base16, Base32, and Base64 algorithms for encoding
and decoding arbitrary binary strings into ASCII-only byte strings that can be
safely sent by email, used as parts of URLs, or included as part of an HTTP
POST request. The encoding algorithm is not the same as the
<strong class="program">uuencode</strong> program.</p>
<p>There are two interfaces provided by this module. The modern interface
supports encoding and decoding ASCII byte string objects using all three
alphabets. The legacy interface provides for encoding and decoding to and from
file-like objects as well as byte strings, but only using the Base64 standard
alphabet.</p>
<p>The modern interface provides:</p>
<dl class="function">
<dt id="base64.b64encode">
<tt class="descclassname">base64.</tt><tt class="descname">b64encode</tt><big>(</big><em>s</em>, <em>altchars=None</em><big>)</big><a class="headerlink" href="#base64.b64encode" title="Permalink to this definition">¶</a></dt>
<dd><p>Encode a byte string using Base64.</p>
<p><em>s</em> is the string to encode. Optional <em>altchars</em> must be a string of at least
length 2 (additional characters are ignored) which specifies an alternative
alphabet for the <tt class="docutils literal"><span class="pre">+</span></tt> and <tt class="docutils literal"><span class="pre">/</span></tt> characters. This allows an application to e.g.
generate URL or filesystem safe Base64 strings. The default is <tt class="xref docutils literal"><span class="pre">None</span></tt>, for
which the standard Base64 alphabet is used.</p>
<p>The encoded byte string is returned.</p>
</dd></dl>
<dl class="function">
<dt id="base64.b64decode">
<tt class="descclassname">base64.</tt><tt class="descname">b64decode</tt><big>(</big><em>s</em>, <em>altchars=None</em>, <em>validate=False</em><big>)</big><a class="headerlink" href="#base64.b64decode" title="Permalink to this definition">¶</a></dt>
<dd><p>Decode a Base64 encoded byte string.</p>
<p><em>s</em> is the byte string to decode. Optional <em>altchars</em> must be a string of
at least length 2 (additional characters are ignored) which specifies the
alternative alphabet used instead of the <tt class="docutils literal"><span class="pre">+</span></tt> and <tt class="docutils literal"><span class="pre">/</span></tt> characters.</p>
<p>The decoded string is returned. A <a class="reference internal" href="binascii.html#binascii.Error" title="binascii.Error"><tt class="xref py py-exc docutils literal"><span class="pre">binascii.Error</span></tt></a> exception is raised
if <em>s</em> is incorrectly padded.</p>
<p>If <em>validate</em> is <tt class="xref docutils literal"><span class="pre">False</span></tt> (the default), non-base64-alphabet characters are
discarded prior to the padding check. If <em>validate</em> is <tt class="xref docutils literal"><span class="pre">True</span></tt>,
non-base64-alphabet characters in the input result in a
<a class="reference internal" href="binascii.html#binascii.Error" title="binascii.Error"><tt class="xref py py-exc docutils literal"><span class="pre">binascii.Error</span></tt></a>.</p>
</dd></dl>
<dl class="function">
<dt id="base64.standard_b64encode">
<tt class="descclassname">base64.</tt><tt class="descname">standard_b64encode</tt><big>(</big><em>s</em><big>)</big><a class="headerlink" href="#base64.standard_b64encode" title="Permalink to this definition">¶</a></dt>
<dd><p>Encode byte string <em>s</em> using the standard Base64 alphabet.</p>
</dd></dl>
<dl class="function">
<dt id="base64.standard_b64decode">
<tt class="descclassname">base64.</tt><tt class="descname">standard_b64decode</tt><big>(</big><em>s</em><big>)</big><a class="headerlink" href="#base64.standard_b64decode" title="Permalink to this definition">¶</a></dt>
<dd><p>Decode byte string <em>s</em> using the standard Base64 alphabet.</p>
</dd></dl>
<dl class="function">
<dt id="base64.urlsafe_b64encode">
<tt class="descclassname">base64.</tt><tt class="descname">urlsafe_b64encode</tt><big>(</big><em>s</em><big>)</big><a class="headerlink" href="#base64.urlsafe_b64encode" title="Permalink to this definition">¶</a></dt>
<dd><p>Encode byte string <em>s</em> using a URL-safe alphabet, which substitutes <tt class="docutils literal"><span class="pre">-</span></tt> instead of
<tt class="docutils literal"><span class="pre">+</span></tt> and <tt class="docutils literal"><span class="pre">_</span></tt> instead of <tt class="docutils literal"><span class="pre">/</span></tt> in the standard Base64 alphabet. The result
can still contain <tt class="docutils literal"><span class="pre">=</span></tt>.</p>
</dd></dl>
<dl class="function">
<dt id="base64.urlsafe_b64decode">
<tt class="descclassname">base64.</tt><tt class="descname">urlsafe_b64decode</tt><big>(</big><em>s</em><big>)</big><a class="headerlink" href="#base64.urlsafe_b64decode" title="Permalink to this definition">¶</a></dt>
<dd><p>Decode byte string <em>s</em> using a URL-safe alphabet, which substitutes <tt class="docutils literal"><span class="pre">-</span></tt> instead of
<tt class="docutils literal"><span class="pre">+</span></tt> and <tt class="docutils literal"><span class="pre">_</span></tt> instead of <tt class="docutils literal"><span class="pre">/</span></tt> in the standard Base64 alphabet.</p>
</dd></dl>
<dl class="function">
<dt id="base64.b32encode">
<tt class="descclassname">base64.</tt><tt class="descname">b32encode</tt><big>(</big><em>s</em><big>)</big><a class="headerlink" href="#base64.b32encode" title="Permalink to this definition">¶</a></dt>
<dd><p>Encode a byte string using Base32. <em>s</em> is the string to encode. The encoded string
is returned.</p>
</dd></dl>
<dl class="function">
<dt id="base64.b32decode">
<tt class="descclassname">base64.</tt><tt class="descname">b32decode</tt><big>(</big><em>s</em>, <em>casefold=False</em>, <em>map01=None</em><big>)</big><a class="headerlink" href="#base64.b32decode" title="Permalink to this definition">¶</a></dt>
<dd><p>Decode a Base32 encoded byte string.</p>
<p><em>s</em> is the byte string to decode. Optional <em>casefold</em> is a flag specifying
whether a lowercase alphabet is acceptable as input. For security purposes,
the default is <tt class="xref docutils literal"><span class="pre">False</span></tt>.</p>
<p><span class="target" id="index-2"></span><a class="rfc reference external" href="http://tools.ietf.org/html/rfc3548.html"><strong>RFC 3548</strong></a> allows for optional mapping of the digit 0 (zero) to the letter O
(oh), and for optional mapping of the digit 1 (one) to either the letter I (eye)
or letter L (el). The optional argument <em>map01</em> when not <tt class="xref docutils literal"><span class="pre">None</span></tt>, specifies
which letter the digit 1 should be mapped to (when <em>map01</em> is not <tt class="xref docutils literal"><span class="pre">None</span></tt>, the
digit 0 is always mapped to the letter O). For security purposes the default is
<tt class="xref docutils literal"><span class="pre">None</span></tt>, so that 0 and 1 are not allowed in the input.</p>
<p>The decoded byte string is returned. A <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><tt class="xref py py-exc docutils literal"><span class="pre">TypeError</span></tt></a> is raised if <em>s</em> were
incorrectly padded or if there are non-alphabet characters present in the
string.</p>
</dd></dl>
<dl class="function">
<dt id="base64.b16encode">
<tt class="descclassname">base64.</tt><tt class="descname">b16encode</tt><big>(</big><em>s</em><big>)</big><a class="headerlink" href="#base64.b16encode" title="Permalink to this definition">¶</a></dt>
<dd><p>Encode a byte string using Base16.</p>
<p><em>s</em> is the string to encode. The encoded byte string is returned.</p>
</dd></dl>
<dl class="function">
<dt id="base64.b16decode">
<tt class="descclassname">base64.</tt><tt class="descname">b16decode</tt><big>(</big><em>s</em>, <em>casefold=False</em><big>)</big><a class="headerlink" href="#base64.b16decode" title="Permalink to this definition">¶</a></dt>
<dd><p>Decode a Base16 encoded byte string.</p>
<p><em>s</em> is the string to decode. Optional <em>casefold</em> is a flag specifying whether a
lowercase alphabet is acceptable as input. For security purposes, the default
is <tt class="xref docutils literal"><span class="pre">False</span></tt>.</p>
<p>The decoded byte string is returned. A <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><tt class="xref py py-exc docutils literal"><span class="pre">TypeError</span></tt></a> is raised if <em>s</em> were
incorrectly padded or if there are non-alphabet characters present in the
string.</p>
</dd></dl>
<p>The legacy interface:</p>
<dl class="function">
<dt id="base64.decode">
<tt class="descclassname">base64.</tt><tt class="descname">decode</tt><big>(</big><em>input</em>, <em>output</em><big>)</big><a class="headerlink" href="#base64.decode" title="Permalink to this definition">¶</a></dt>
<dd><p>Decode the contents of the binary <em>input</em> file and write the resulting binary
data to the <em>output</em> file. <em>input</em> and <em>output</em> must be <a class="reference internal" href="../glossary.html#term-file-object"><em class="xref std std-term">file objects</em></a>. <em>input</em> will be read until <tt class="docutils literal"><span class="pre">input.read()</span></tt> returns an empty
bytes object.</p>
</dd></dl>
<dl class="function">
<dt id="base64.decodebytes">
<tt class="descclassname">base64.</tt><tt class="descname">decodebytes</tt><big>(</big><em>s</em><big>)</big><a class="headerlink" href="#base64.decodebytes" title="Permalink to this definition">¶</a></dt>
<dt id="base64.decodestring">
<tt class="descclassname">base64.</tt><tt class="descname">decodestring</tt><big>(</big><em>s</em><big>)</big><a class="headerlink" href="#base64.decodestring" title="Permalink to this definition">¶</a></dt>
<dd><p>Decode the byte string <em>s</em>, which must contain one or more lines of base64
encoded data, and return a byte string containing the resulting binary data.
<tt class="docutils literal"><span class="pre">decodestring</span></tt> is a deprecated alias.</p>
</dd></dl>
<dl class="function">
<dt id="base64.encode">
<tt class="descclassname">base64.</tt><tt class="descname">encode</tt><big>(</big><em>input</em>, <em>output</em><big>)</big><a class="headerlink" href="#base64.encode" title="Permalink to this definition">¶</a></dt>
<dd><p>Encode the contents of the binary <em>input</em> file and write the resulting base64
encoded data to the <em>output</em> file. <em>input</em> and <em>output</em> must be <a class="reference internal" href="../glossary.html#term-file-object"><em class="xref std std-term">file
objects</em></a>. <em>input</em> will be read until <tt class="docutils literal"><span class="pre">input.read()</span></tt> returns
an empty bytes object. <a class="reference internal" href="#base64.encode" title="base64.encode"><tt class="xref py py-func docutils literal"><span class="pre">encode()</span></tt></a> returns the encoded data plus a trailing
newline character (<tt class="docutils literal"><span class="pre">b'\n'</span></tt>).</p>
</dd></dl>
<dl class="function">
<dt id="base64.encodebytes">
<tt class="descclassname">base64.</tt><tt class="descname">encodebytes</tt><big>(</big><em>s</em><big>)</big><a class="headerlink" href="#base64.encodebytes" title="Permalink to this definition">¶</a></dt>
<dt id="base64.encodestring">
<tt class="descclassname">base64.</tt><tt class="descname">encodestring</tt><big>(</big><em>s</em><big>)</big><a class="headerlink" href="#base64.encodestring" title="Permalink to this definition">¶</a></dt>
<dd><p>Encode the byte string <em>s</em>, which can contain arbitrary binary data, and
return a byte string containing one or more lines of base64-encoded data.
<a class="reference internal" href="#base64.encodebytes" title="base64.encodebytes"><tt class="xref py py-func docutils literal"><span class="pre">encodebytes()</span></tt></a> returns a string containing one or more lines of
base64-encoded data always including an extra trailing newline (<tt class="docutils literal"><span class="pre">b'\n'</span></tt>).
<tt class="docutils literal"><span class="pre">encodestring</span></tt> is a deprecated alias.</p>
</dd></dl>
<p>An example usage of the module:</p>
<div class="highlight-python3"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">base64</span>
<span class="gp">>>> </span><span class="n">encoded</span> <span class="o">=</span> <span class="n">base64</span><span class="o">.</span><span class="n">b64encode</span><span class="p">(</span><span class="n">b</span><span class="s">'data to be encoded'</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">encoded</span>
<span class="go">b'ZGF0YSB0byBiZSBlbmNvZGVk'</span>
<span class="gp">>>> </span><span class="n">data</span> <span class="o">=</span> <span class="n">base64</span><span class="o">.</span><span class="n">b64decode</span><span class="p">(</span><span class="n">encoded</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">data</span>
<span class="go">b'data to be encoded'</span>
</pre></div>
</div>
<div class="admonition-see-also admonition seealso">
<p class="first admonition-title">See also</p>
<dl class="last docutils">
<dt>Module <a class="reference internal" href="binascii.html#module-binascii" title="binascii: Tools for converting between binary and various ASCII-encoded binary representations."><tt class="xref py py-mod docutils literal"><span class="pre">binascii</span></tt></a></dt>
<dd>Support module containing ASCII-to-binary and binary-to-ASCII conversions.</dd>
<dt><span class="target" id="index-3"></span><a class="rfc reference external" href="http://tools.ietf.org/html/rfc1521.html"><strong>RFC 1521</strong></a> - MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies</dt>
<dd>Section 5.2, “Base64 Content-Transfer-Encoding,” provides the definition of the
base64 encoding.</dd>
</dl>
</div>
</div>
</div>
</div>
</div>
<div class="sphinxsidebar">
<div class="sphinxsidebarwrapper">
<h4>Previous topic</h4>
<p class="topless"><a href="mimetypes.html"
title="previous chapter">18.5. <tt class="docutils literal"><span class="pre">mimetypes</span></tt> — Map filenames to MIME types</a></p>
<h4>Next topic</h4>
<p class="topless"><a href="binhex.html"
title="next chapter">18.7. <tt class="docutils literal"><span class="pre">binhex</span></tt> — Encode and decode binhex4 files</a></p>
<h3>This Page</h3>
<ul class="this-page-menu">
<li><a href="../bugs.html">Report a Bug</a></li>
<li><a href="../_sources/library/base64.txt"
rel="nofollow">Show Source</a></li>
</ul>
<div id="searchbox" style="display: none">
<h3>Quick search</h3>
<form class="search" action="../search.html" method="get">
<input type="text" name="q" size="18" />
<input type="submit" value="Go" />
<input type="hidden" name="check_keywords" value="yes" />
<input type="hidden" name="area" value="default" />
</form>
<p class="searchtip" style="font-size: 90%">
Enter search terms or a module, class or function name.
</p>
</div>
<script type="text/javascript">$('#searchbox').show(0);</script>
</div>
</div>
<div class="clearer"></div>
</div>
<div class="related">
<h3>Navigation</h3>
<ul>
<li class="right" style="margin-right: 10px">
<a href="../genindex.html" title="General Index"
>index</a></li>
<li class="right" >
<a href="../py-modindex.html" title="Python Module Index"
>modules</a> |</li>
<li class="right" >
<a href="binhex.html" title="18.7. binhex — Encode and decode binhex4 files"
>next</a> |</li>
<li class="right" >
<a href="mimetypes.html" title="18.5. mimetypes — Map filenames to MIME types"
>previous</a> |</li>
<li><img src="../_static/py.png" alt=""
style="vertical-align: middle; margin-top: -1px"/></li>
<li><a href="../index.html">Python v3.2.2 documentation</a> »</li>
<li><a href="index.html" >The Python Standard Library</a> »</li>
<li><a href="netdata.html" >18. Internet Data Handling</a> »</li>
</ul>
</div>
<div class="footer">
© <a href="../copyright.html">Copyright</a> 1990-2011, Python Software Foundation.
<br />
The Python Software Foundation is a non-profit corporation.
<a href="http://www.python.org/psf/donations/">Please donate.</a>
<br />
Last updated on Sep 04, 2011.
<a href="../bugs.html">Found a bug</a>?
<br />
Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 1.0.7.
</div>
</body>
</html>
distrib
>
Mandriva
>
2010.1
>
x86_64
>
media
>
contrib-backports
>
by-pkgid
>
3ba3bd1608c672ba2129b098a48e9e4d
>
files
>
619
