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<!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="X-UA-Compatible" content="IE=Edge" /> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>18.14. binascii — Convert between binary and ASCII — Python 2.7.18 documentation</title> <link rel="stylesheet" href="../_static/classic.css" type="text/css" /> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> <script type="text/javascript" id="documentation_options" data-url_root="../" src="../_static/documentation_options.js"></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/language_data.js"></script> <script type="text/javascript" src="../_static/sidebar.js"></script> <link rel="search" type="application/opensearchdescription+xml" title="Search within Python 2.7.18 documentation" href="../_static/opensearch.xml"/> <link rel="author" title="About these documents" href="../about.html" /> <link rel="index" title="Index" href="../genindex.html" /> <link rel="search" title="Search" href="../search.html" /> <link rel="copyright" title="Copyright" href="../copyright.html" /> <link rel="next" title="18.15. quopri — Encode and decode MIME quoted-printable data" href="quopri.html" /> <link rel="prev" title="18.13. binhex — Encode and decode binhex4 files" href="binhex.html" /> <link rel="shortcut icon" type="image/png" href="../_static/py.png" /> <link rel="canonical" href="file:///usr/share/doc/python2.7/html/library/binascii.html" /> <script type="text/javascript" src="../_static/copybutton.js"></script> </head><body> <div id="outdated-warning" style="padding: .5em; text-align: center; background-color: #FFBABA; color: #6A0E0E;"> This document is for an old version of Python that is <a href="https://devguide.python.org/devcycle/#end-of-life-branches">no longer supported</a>. You should install the python3 and python3-doc packages and read the <a href="file:///usr/share/doc/python3-doc/html/library/binascii.html"> Python documentation for the Python3 version packaged in this release</a>. </div> <div class="related" role="navigation" aria-label="related navigation"> <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="quopri.html" title="18.15. quopri — Encode and decode MIME quoted-printable data" accesskey="N">next</a> |</li> <li class="right" > <a href="binhex.html" title="18.13. binhex — Encode and decode binhex4 files" accesskey="P">previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="https://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.18 documentation</a> » </li> <li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> »</li> <li class="nav-item nav-item-2"><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" role="main"> <div class="section" id="module-binascii"> <span id="binascii-convert-between-binary-and-ascii"></span><h1>18.14. <a class="reference internal" href="#module-binascii" title="binascii: Tools for converting between binary and various ASCII-encoded binary representations."><code class="xref py py-mod docutils literal notranslate"><span class="pre">binascii</span></code></a> — Convert between binary and ASCII<a class="headerlink" href="#module-binascii" title="Permalink to this headline">¶</a></h1> <p id="index-0">The <a class="reference internal" href="#module-binascii" title="binascii: Tools for converting between binary and various ASCII-encoded binary representations."><code class="xref py py-mod docutils literal notranslate"><span class="pre">binascii</span></code></a> module contains a number of methods to convert between binary and various ASCII-encoded binary representations. Normally, you will not use these functions directly but use wrapper modules like <a class="reference internal" href="uu.html#module-uu" title="uu: Encode and decode files in uuencode format."><code class="xref py py-mod docutils literal notranslate"><span class="pre">uu</span></code></a>, <a class="reference internal" href="base64.html#module-base64" title="base64: RFC 3548: Base16, Base32, Base64 Data Encodings"><code class="xref py py-mod docutils literal notranslate"><span class="pre">base64</span></code></a>, or <a class="reference internal" href="binhex.html#module-binhex" title="binhex: Encode and decode files in binhex4 format."><code class="xref py py-mod docutils literal notranslate"><span class="pre">binhex</span></code></a> instead. The <a class="reference internal" href="#module-binascii" title="binascii: Tools for converting between binary and various ASCII-encoded binary representations."><code class="xref py py-mod docutils literal notranslate"><span class="pre">binascii</span></code></a> module contains low-level functions written in C for greater speed that are used by the higher-level modules.</p> <p>The <a class="reference internal" href="#module-binascii" title="binascii: Tools for converting between binary and various ASCII-encoded binary representations."><code class="xref py py-mod docutils literal notranslate"><span class="pre">binascii</span></code></a> module defines the following functions:</p> <dl class="function"> <dt id="binascii.a2b_uu"> <code class="descclassname">binascii.</code><code class="descname">a2b_uu</code><span class="sig-paren">(</span><em>string</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.a2b_uu" title="Permalink to this definition">¶</a></dt> <dd><p>Convert a single line of uuencoded data back to binary and return the binary data. Lines normally contain 45 (binary) bytes, except for the last line. Line data may be followed by whitespace.</p> </dd></dl> <dl class="function"> <dt id="binascii.b2a_uu"> <code class="descclassname">binascii.</code><code class="descname">b2a_uu</code><span class="sig-paren">(</span><em>data</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.b2a_uu" title="Permalink to this definition">¶</a></dt> <dd><p>Convert binary data to a line of ASCII characters, the return value is the converted line, including a newline char. The length of <em>data</em> should be at most 45.</p> </dd></dl> <dl class="function"> <dt id="binascii.a2b_base64"> <code class="descclassname">binascii.</code><code class="descname">a2b_base64</code><span class="sig-paren">(</span><em>string</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.a2b_base64" title="Permalink to this definition">¶</a></dt> <dd><p>Convert a block of base64 data back to binary and return the binary data. More than one line may be passed at a time.</p> </dd></dl> <dl class="function"> <dt id="binascii.b2a_base64"> <code class="descclassname">binascii.</code><code class="descname">b2a_base64</code><span class="sig-paren">(</span><em>data</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.b2a_base64" title="Permalink to this definition">¶</a></dt> <dd><p>Convert binary data to a line of ASCII characters in base64 coding. The return value is the converted line, including a newline char. The newline is added because the original use case for this function was to feed it a series of 57 byte input lines to get output lines that conform to the MIME-base64 standard. Otherwise the output conforms to <span class="target" id="index-1"></span><a class="rfc reference external" href="https://tools.ietf.org/html/rfc3548.html"><strong>RFC 3548</strong></a>.</p> </dd></dl> <dl class="function"> <dt id="binascii.a2b_qp"> <code class="descclassname">binascii.</code><code class="descname">a2b_qp</code><span class="sig-paren">(</span><em>string</em><span class="optional">[</span>, <em>header</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#binascii.a2b_qp" title="Permalink to this definition">¶</a></dt> <dd><p>Convert a block of quoted-printable data back to binary and return the binary data. More than one line may be passed at a time. If the optional argument <em>header</em> is present and true, underscores will be decoded as spaces.</p> </dd></dl> <dl class="function"> <dt id="binascii.b2a_qp"> <code class="descclassname">binascii.</code><code class="descname">b2a_qp</code><span class="sig-paren">(</span><em>data</em><span class="optional">[</span>, <em>quotetabs</em>, <em>istext</em>, <em>header</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#binascii.b2a_qp" title="Permalink to this definition">¶</a></dt> <dd><p>Convert binary data to a line(s) of ASCII characters in quoted-printable encoding. The return value is the converted line(s). If the optional argument <em>quotetabs</em> is present and true, all tabs and spaces will be encoded. If the optional argument <em>istext</em> is present and true, newlines are not encoded but trailing whitespace will be encoded. If the optional argument <em>header</em> is present and true, spaces will be encoded as underscores per RFC1522. If the optional argument <em>header</em> is present and false, newline characters will be encoded as well; otherwise linefeed conversion might corrupt the binary data stream.</p> </dd></dl> <dl class="function"> <dt id="binascii.a2b_hqx"> <code class="descclassname">binascii.</code><code class="descname">a2b_hqx</code><span class="sig-paren">(</span><em>string</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.a2b_hqx" title="Permalink to this definition">¶</a></dt> <dd><p>Convert binhex4 formatted ASCII data to binary, without doing RLE-decompression. The string should contain a complete number of binary bytes, or (in case of the last portion of the binhex4 data) have the remaining bits zero.</p> </dd></dl> <dl class="function"> <dt id="binascii.rledecode_hqx"> <code class="descclassname">binascii.</code><code class="descname">rledecode_hqx</code><span class="sig-paren">(</span><em>data</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.rledecode_hqx" title="Permalink to this definition">¶</a></dt> <dd><p>Perform RLE-decompression on the data, as per the binhex4 standard. The algorithm uses <code class="docutils literal notranslate"><span class="pre">0x90</span></code> after a byte as a repeat indicator, followed by a count. A count of <code class="docutils literal notranslate"><span class="pre">0</span></code> specifies a byte value of <code class="docutils literal notranslate"><span class="pre">0x90</span></code>. The routine returns the decompressed data, unless data input data ends in an orphaned repeat indicator, in which case the <a class="reference internal" href="#binascii.Incomplete" title="binascii.Incomplete"><code class="xref py py-exc docutils literal notranslate"><span class="pre">Incomplete</span></code></a> exception is raised.</p> </dd></dl> <dl class="function"> <dt id="binascii.rlecode_hqx"> <code class="descclassname">binascii.</code><code class="descname">rlecode_hqx</code><span class="sig-paren">(</span><em>data</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.rlecode_hqx" title="Permalink to this definition">¶</a></dt> <dd><p>Perform binhex4 style RLE-compression on <em>data</em> and return the result.</p> </dd></dl> <dl class="function"> <dt id="binascii.b2a_hqx"> <code class="descclassname">binascii.</code><code class="descname">b2a_hqx</code><span class="sig-paren">(</span><em>data</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.b2a_hqx" title="Permalink to this definition">¶</a></dt> <dd><p>Perform hexbin4 binary-to-ASCII translation and return the resulting string. The argument should already be RLE-coded, and have a length divisible by 3 (except possibly the last fragment).</p> </dd></dl> <dl class="function"> <dt id="binascii.crc_hqx"> <code class="descclassname">binascii.</code><code class="descname">crc_hqx</code><span class="sig-paren">(</span><em>data</em>, <em>crc</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.crc_hqx" title="Permalink to this definition">¶</a></dt> <dd><p>Compute a 16-bit CRC value of <em>data</em>, starting with an initial <em>crc</em> and returning the result. This uses the CRC-CCITT polynomial <em>x</em><sup>16</sup> + <em>x</em><sup>12</sup> + <em>x</em><sup>5</sup> + 1, often represented as 0x1021. This CRC is used in the binhex4 format.</p> </dd></dl> <dl class="function"> <dt id="binascii.crc32"> <code class="descclassname">binascii.</code><code class="descname">crc32</code><span class="sig-paren">(</span><em>data</em><span class="optional">[</span>, <em>crc</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#binascii.crc32" title="Permalink to this definition">¶</a></dt> <dd><p>Compute CRC-32, the 32-bit checksum of data, starting with an initial crc. This is consistent with the ZIP file checksum. Since the algorithm is designed for use as a checksum algorithm, it is not suitable for use as a general hash algorithm. Use as follows:</p> <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="nb">print</span> <span class="n">binascii</span><span class="o">.</span><span class="n">crc32</span><span class="p">(</span><span class="s2">"hello world"</span><span class="p">)</span> <span class="c1"># Or, in two pieces:</span> <span class="n">crc</span> <span class="o">=</span> <span class="n">binascii</span><span class="o">.</span><span class="n">crc32</span><span class="p">(</span><span class="s2">"hello"</span><span class="p">)</span> <span class="n">crc</span> <span class="o">=</span> <span class="n">binascii</span><span class="o">.</span><span class="n">crc32</span><span class="p">(</span><span class="s2">" world"</span><span class="p">,</span> <span class="n">crc</span><span class="p">)</span> <span class="o">&</span> <span class="mh">0xffffffff</span> <span class="nb">print</span> <span class="s1">'crc32 = 0x</span><span class="si">%08x</span><span class="s1">'</span> <span class="o">%</span> <span class="n">crc</span> </pre></div> </div> </dd></dl> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">To generate the same numeric value across all Python versions and platforms use crc32(data) & 0xffffffff. If you are only using the checksum in packed binary format this is not necessary as the return value is the correct 32bit binary representation regardless of sign.</p> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 2.6: </span>The return value is in the range [-2**31, 2**31-1] regardless of platform. In the past the value would be signed on some platforms and unsigned on others. Use & 0xffffffff on the value if you want it to match Python 3 behavior.</p> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.0: </span>The return value is unsigned and in the range [0, 2**32-1] regardless of platform.</p> </div> <dl class="function"> <dt id="binascii.b2a_hex"> <code class="descclassname">binascii.</code><code class="descname">b2a_hex</code><span class="sig-paren">(</span><em>data</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.b2a_hex" title="Permalink to this definition">¶</a></dt> <dt id="binascii.hexlify"> <code class="descclassname">binascii.</code><code class="descname">hexlify</code><span class="sig-paren">(</span><em>data</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.hexlify" title="Permalink to this definition">¶</a></dt> <dd><p>Return the hexadecimal representation of the binary <em>data</em>. Every byte of <em>data</em> is converted into the corresponding 2-digit hex representation. The resulting string is therefore twice as long as the length of <em>data</em>.</p> </dd></dl> <dl class="function"> <dt id="binascii.a2b_hex"> <code class="descclassname">binascii.</code><code class="descname">a2b_hex</code><span class="sig-paren">(</span><em>hexstr</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.a2b_hex" title="Permalink to this definition">¶</a></dt> <dt id="binascii.unhexlify"> <code class="descclassname">binascii.</code><code class="descname">unhexlify</code><span class="sig-paren">(</span><em>hexstr</em><span class="sig-paren">)</span><a class="headerlink" href="#binascii.unhexlify" title="Permalink to this definition">¶</a></dt> <dd><p>Return the binary data represented by the hexadecimal string <em>hexstr</em>. This function is the inverse of <a class="reference internal" href="#binascii.b2a_hex" title="binascii.b2a_hex"><code class="xref py py-func docutils literal notranslate"><span class="pre">b2a_hex()</span></code></a>. <em>hexstr</em> must contain an even number of hexadecimal digits (which can be upper or lower case), otherwise a <a class="reference internal" href="exceptions.html#exceptions.TypeError" title="exceptions.TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a> is raised.</p> </dd></dl> <dl class="exception"> <dt id="binascii.Error"> <em class="property">exception </em><code class="descclassname">binascii.</code><code class="descname">Error</code><a class="headerlink" href="#binascii.Error" title="Permalink to this definition">¶</a></dt> <dd><p>Exception raised on errors. These are usually programming errors.</p> </dd></dl> <dl class="exception"> <dt id="binascii.Incomplete"> <em class="property">exception </em><code class="descclassname">binascii.</code><code class="descname">Incomplete</code><a class="headerlink" href="#binascii.Incomplete" title="Permalink to this definition">¶</a></dt> <dd><p>Exception raised on incomplete data. These are usually not programming errors, but may be handled by reading a little more data and trying again.</p> </dd></dl> <div class="admonition seealso"> <p class="first admonition-title">See also</p> <dl class="last docutils"> <dt>Module <a class="reference internal" href="base64.html#module-base64" title="base64: RFC 3548: Base16, Base32, Base64 Data Encodings"><code class="xref py py-mod docutils literal notranslate"><span class="pre">base64</span></code></a></dt> <dd>Support for RFC compliant base64-style encoding in base 16, 32, and 64.</dd> <dt>Module <a class="reference internal" href="binhex.html#module-binhex" title="binhex: Encode and decode files in binhex4 format."><code class="xref py py-mod docutils literal notranslate"><span class="pre">binhex</span></code></a></dt> <dd>Support for the binhex format used on the Macintosh.</dd> <dt>Module <a class="reference internal" href="uu.html#module-uu" title="uu: Encode and decode files in uuencode format."><code class="xref py py-mod docutils literal notranslate"><span class="pre">uu</span></code></a></dt> <dd>Support for UU encoding used on Unix.</dd> <dt>Module <a class="reference internal" href="quopri.html#module-quopri" title="quopri: Encode and decode files using the MIME quoted-printable encoding."><code class="xref py py-mod docutils literal notranslate"><span class="pre">quopri</span></code></a></dt> <dd>Support for quoted-printable encoding used in MIME email messages.</dd> </dl> </div> </div> </div> </div> </div> <div class="sphinxsidebar" role="navigation" aria-label="main navigation"> <div class="sphinxsidebarwrapper"> <h4>Previous topic</h4> <p class="topless"><a href="binhex.html" title="previous chapter">18.13. <code class="docutils literal notranslate"><span class="pre">binhex</span></code> — Encode and decode binhex4 files</a></p> <h4>Next topic</h4> <p class="topless"><a href="quopri.html" title="next chapter">18.15. <code class="docutils literal notranslate"><span class="pre">quopri</span></code> — Encode and decode MIME quoted-printable data</a></p> <div role="note" aria-label="source link"> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../_sources/library/binascii.rst.txt" rel="nofollow">Show Source</a></li> </ul> </div> <div id="searchbox" style="display: none" role="search"> <h3>Quick search</h3> <div class="searchformwrapper"> <form class="search" action="../search.html" method="get"> <input type="text" name="q" /> <input type="submit" value="Go" /> <input type="hidden" name="check_keywords" value="yes" /> <input type="hidden" name="area" value="default" /> </form> </div> </div> <script type="text/javascript">$('#searchbox').show(0);</script> </div> </div> <div class="clearer"></div> </div> <div class="related" role="navigation" aria-label="related navigation"> <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="quopri.html" title="18.15. quopri — Encode and decode MIME quoted-printable data" >next</a> |</li> <li class="right" > <a href="binhex.html" title="18.13. binhex — Encode and decode binhex4 files" >previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="https://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.18 documentation</a> » </li> <li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> »</li> <li class="nav-item nav-item-2"><a href="netdata.html" >18. 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