Edit File: email.header.html
<!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>18.1.5. email: Internationalized headers — Python v2.6.6 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: '2.6.6', COLLAPSE_MODINDEX: false, FILE_SUFFIX: '.html', HAS_SOURCE: true }; </script> <script type="text/javascript" src="../_static/jquery.js"></script> <script type="text/javascript" src="../_static/doctools.js"></script> <link rel="search" type="application/opensearchdescription+xml" title="Search within Python v2.6.6 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 v2.6.6 documentation" href="../index.html" /> <link rel="up" title="18.1. email — An email and MIME handling package" href="email.html" /> <link rel="next" title="18.1.6. email: Representing character sets" href="email.charset.html" /> <link rel="prev" title="18.1.4. email: Creating email and MIME objects from scratch" href="email.mime.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="../modindex.html" title="Global Module Index" accesskey="M">modules</a> |</li> <li class="right" > <a href="email.charset.html" title="18.1.6. email: Representing character sets" accesskey="N">next</a> |</li> <li class="right" > <a href="email.mime.html" title="18.1.4. email: Creating email and MIME objects from scratch" 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 v2.6.6 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> <li><a href="email.html" accesskey="U">18.1. <tt class="docutils literal docutils literal docutils literal docutils literal docutils literal docutils literal docutils literal"><span class="pre">email</span></tt> — An email and MIME handling package</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body"> <div class="section" id="module-email.header"> <h1>18.1.5. <a title="Package supporting the parsing, manipulating, and generating email messages, including MIME documents." class="reference external" href="email.html#module-email"><tt class="xref docutils literal"><span class="pre">email</span></tt></a>: Internationalized headers<a class="headerlink" href="#module-email.header" title="Permalink to this headline">¶</a></h1> <p><span class="target" id="index-295"></span><a class="reference external" href="http://tools.ietf.org/html/rfc2822.html"><strong>RFC 2822</strong></a> is the base standard that describes the format of email messages. It derives from the older <span class="target" id="index-296"></span><a class="reference external" href="http://tools.ietf.org/html/rfc822.html"><strong>RFC 822</strong></a> standard which came into widespread use at a time when most email was composed of ASCII characters only. <span class="target" id="index-297"></span><a class="reference external" href="http://tools.ietf.org/html/rfc2822.html"><strong>RFC 2822</strong></a> is a specification written assuming email contains only 7-bit ASCII characters.</p> <p>Of course, as email has been deployed worldwide, it has become internationalized, such that language specific character sets can now be used in email messages. The base standard still requires email messages to be transferred using only 7-bit ASCII characters, so a slew of RFCs have been written describing how to encode email containing non-ASCII characters into <span class="target" id="index-298"></span><a class="reference external" href="http://tools.ietf.org/html/rfc2822.html"><strong>RFC 2822</strong></a>-compliant format. These RFCs include <span class="target" id="index-299"></span><a class="reference external" href="http://tools.ietf.org/html/rfc2045.html"><strong>RFC 2045</strong></a>, <span class="target" id="index-300"></span><a class="reference external" href="http://tools.ietf.org/html/rfc2046.html"><strong>RFC 2046</strong></a>, <span class="target" id="index-301"></span><a class="reference external" href="http://tools.ietf.org/html/rfc2047.html"><strong>RFC 2047</strong></a>, and <span class="target" id="index-302"></span><a class="reference external" href="http://tools.ietf.org/html/rfc2231.html"><strong>RFC 2231</strong></a>. The <a title="Package supporting the parsing, manipulating, and generating email messages, including MIME documents." class="reference external" href="email.html#module-email"><tt class="xref docutils literal"><span class="pre">email</span></tt></a> package supports these standards in its <tt class="xref docutils literal"><span class="pre">email.header</span></tt> and <a title="Character Sets" class="reference external" href="email.charset.html#module-email.charset"><tt class="xref docutils literal"><span class="pre">email.charset</span></tt></a> modules.</p> <p>If you want to include non-ASCII characters in your email headers, say in the <em>Subject</em> or <em>To</em> fields, you should use the <a title="email.header.Header" class="reference internal" href="#email.header.Header"><tt class="xref docutils literal"><span class="pre">Header</span></tt></a> class and assign the field in the <a title="email.message.Message" class="reference external" href="email.message.html#email.message.Message"><tt class="xref docutils literal"><span class="pre">Message</span></tt></a> object to an instance of <a title="email.header.Header" class="reference internal" href="#email.header.Header"><tt class="xref docutils literal"><span class="pre">Header</span></tt></a> instead of using a string for the header value. Import the <a title="email.header.Header" class="reference internal" href="#email.header.Header"><tt class="xref docutils literal"><span class="pre">Header</span></tt></a> class from the <tt class="xref docutils literal"><span class="pre">email.header</span></tt> module. For example:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">email.message</span> <span class="kn">import</span> <span class="n">Message</span> <span class="gp">>>> </span><span class="kn">from</span> <span class="nn">email.header</span> <span class="kn">import</span> <span class="n">Header</span> <span class="gp">>>> </span><span class="n">msg</span> <span class="o">=</span> <span class="n">Message</span><span class="p">()</span> <span class="gp">>>> </span><span class="n">h</span> <span class="o">=</span> <span class="n">Header</span><span class="p">(</span><span class="s">'p</span><span class="se">\xf6</span><span class="s">stal'</span><span class="p">,</span> <span class="s">'iso-8859-1'</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">msg</span><span class="p">[</span><span class="s">'Subject'</span><span class="p">]</span> <span class="o">=</span> <span class="n">h</span> <span class="gp">>>> </span><span class="k">print</span> <span class="n">msg</span><span class="o">.</span><span class="n">as_string</span><span class="p">()</span> <span class="go">Subject: =?iso-8859-1?q?p=F6stal?=</span> </pre></div> </div> <p>Notice here how we wanted the <em>Subject</em> field to contain a non-ASCII character? We did this by creating a <a title="email.header.Header" class="reference internal" href="#email.header.Header"><tt class="xref docutils literal"><span class="pre">Header</span></tt></a> instance and passing in the character set that the byte string was encoded in. When the subsequent <a title="email.message.Message" class="reference external" href="email.message.html#email.message.Message"><tt class="xref docutils literal"><span class="pre">Message</span></tt></a> instance was flattened, the <em>Subject</em> field was properly <span class="target" id="index-303"></span><a class="reference external" href="http://tools.ietf.org/html/rfc2047.html"><strong>RFC 2047</strong></a> encoded. MIME-aware mail readers would show this header using the embedded ISO-8859-1 character.</p> <p class="versionadded"> <span class="versionmodified">New in version 2.2.2.</span></p> <p>Here is the <a title="email.header.Header" class="reference internal" href="#email.header.Header"><tt class="xref docutils literal"><span class="pre">Header</span></tt></a> class description:</p> <dl class="class"> <dt id="email.header.Header"> <em class="property">class </em><tt class="descclassname">email.header.</tt><tt class="descname">Header</tt><big>(</big><span class="optional">[</span><em>s</em><span class="optional">[</span>, <em>charset</em><span class="optional">[</span>, <em>maxlinelen</em><span class="optional">[</span>, <em>header_name</em><span class="optional">[</span>, <em>continuation_ws</em><span class="optional">[</span>, <em>errors</em><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><big>)</big><a class="headerlink" href="#email.header.Header" title="Permalink to this definition">¶</a></dt> <dd><p>Create a MIME-compliant header that can contain strings in different character sets.</p> <p>Optional <em>s</em> is the initial header value. If <tt class="xref docutils literal"><span class="pre">None</span></tt> (the default), the initial header value is not set. You can later append to the header with <a title="email.header.Header.append" class="reference internal" href="#email.header.Header.append"><tt class="xref docutils literal"><span class="pre">append()</span></tt></a> method calls. <em>s</em> may be a byte string or a Unicode string, but see the <a title="email.header.Header.append" class="reference internal" href="#email.header.Header.append"><tt class="xref docutils literal"><span class="pre">append()</span></tt></a> documentation for semantics.</p> <p>Optional <em>charset</em> serves two purposes: it has the same meaning as the <em>charset</em> argument to the <a title="email.header.Header.append" class="reference internal" href="#email.header.Header.append"><tt class="xref docutils literal"><span class="pre">append()</span></tt></a> method. It also sets the default character set for all subsequent <a title="email.header.Header.append" class="reference internal" href="#email.header.Header.append"><tt class="xref docutils literal"><span class="pre">append()</span></tt></a> calls that omit the <em>charset</em> argument. If <em>charset</em> is not provided in the constructor (the default), the <tt class="docutils literal"><span class="pre">us-ascii</span></tt> character set is used both as <em>s</em>‘s initial charset and as the default for subsequent <a title="email.header.Header.append" class="reference internal" href="#email.header.Header.append"><tt class="xref docutils literal"><span class="pre">append()</span></tt></a> calls.</p> <p>The maximum line length can be specified explicit via <em>maxlinelen</em>. For splitting the first line to a shorter value (to account for the field header which isn’t included in <em>s</em>, e.g. <em>Subject</em>) pass in the name of the field in <em>header_name</em>. The default <em>maxlinelen</em> is 76, and the default value for <em>header_name</em> is <tt class="xref docutils literal"><span class="pre">None</span></tt>, meaning it is not taken into account for the first line of a long, split header.</p> <p>Optional <em>continuation_ws</em> must be <span class="target" id="index-304"></span><a class="reference external" href="http://tools.ietf.org/html/rfc2822.html"><strong>RFC 2822</strong></a>-compliant folding whitespace, and is usually either a space or a hard tab character. This character will be prepended to continuation lines.</p> <p>Optional <em>errors</em> is passed straight through to the <a title="email.header.Header.append" class="reference internal" href="#email.header.Header.append"><tt class="xref docutils literal"><span class="pre">append()</span></tt></a> method.</p> <dl class="method"> <dt id="email.header.Header.append"> <tt class="descname">append</tt><big>(</big><em>s</em><span class="optional">[</span>, <em>charset</em><span class="optional">[</span>, <em>errors</em><span class="optional">]</span><span class="optional">]</span><big>)</big><a class="headerlink" href="#email.header.Header.append" title="Permalink to this definition">¶</a></dt> <dd><p>Append the string <em>s</em> to the MIME header.</p> <p>Optional <em>charset</em>, if given, should be a <a title="email.charset.Charset" class="reference external" href="email.charset.html#email.charset.Charset"><tt class="xref docutils literal"><span class="pre">Charset</span></tt></a> instance (see <a title="Character Sets" class="reference external" href="email.charset.html#module-email.charset"><tt class="xref docutils literal"><span class="pre">email.charset</span></tt></a>) or the name of a character set, which will be converted to a <a title="email.charset.Charset" class="reference external" href="email.charset.html#email.charset.Charset"><tt class="xref docutils literal"><span class="pre">Charset</span></tt></a> instance. A value of <tt class="xref docutils literal"><span class="pre">None</span></tt> (the default) means that the <em>charset</em> given in the constructor is used.</p> <p><em>s</em> may be a byte string or a Unicode string. If it is a byte string (i.e. <tt class="docutils literal"><span class="pre">isinstance(s,</span> <span class="pre">str)</span></tt> is true), then <em>charset</em> is the encoding of that byte string, and a <a title="exceptions.UnicodeError" class="reference external" href="exceptions.html#exceptions.UnicodeError"><tt class="xref docutils literal"><span class="pre">UnicodeError</span></tt></a> will be raised if the string cannot be decoded with that character set.</p> <p>If <em>s</em> is a Unicode string, then <em>charset</em> is a hint specifying the character set of the characters in the string. In this case, when producing an <span class="target" id="index-305"></span><a class="reference external" href="http://tools.ietf.org/html/rfc2822.html"><strong>RFC 2822</strong></a>-compliant header using <span class="target" id="index-306"></span><a class="reference external" href="http://tools.ietf.org/html/rfc2047.html"><strong>RFC 2047</strong></a> rules, the Unicode string will be encoded using the following charsets in order: <tt class="docutils literal"><span class="pre">us-ascii</span></tt>, the <em>charset</em> hint, <tt class="docutils literal"><span class="pre">utf-8</span></tt>. The first character set to not provoke a <a title="exceptions.UnicodeError" class="reference external" href="exceptions.html#exceptions.UnicodeError"><tt class="xref docutils literal"><span class="pre">UnicodeError</span></tt></a> is used.</p> <p>Optional <em>errors</em> is passed through to any <a title="unicode" class="reference external" href="functions.html#unicode"><tt class="xref docutils literal"><span class="pre">unicode()</span></tt></a> or <tt class="xref docutils literal"><span class="pre">ustr.encode()</span></tt> call, and defaults to “strict”.</p> </dd></dl> <dl class="method"> <dt id="email.header.Header.encode"> <tt class="descname">encode</tt><big>(</big><span class="optional">[</span><em>splitchars</em><span class="optional">]</span><big>)</big><a class="headerlink" href="#email.header.Header.encode" title="Permalink to this definition">¶</a></dt> <dd>Encode a message header into an RFC-compliant format, possibly wrapping long lines and encapsulating non-ASCII parts in base64 or quoted-printable encodings. Optional <em>splitchars</em> is a string containing characters to split long ASCII lines on, in rough support of <span class="target" id="index-307"></span><a class="reference external" href="http://tools.ietf.org/html/rfc2822.html"><strong>RFC 2822</strong></a>‘s <em>highest level syntactic breaks</em>. This doesn’t affect <span class="target" id="index-308"></span><a class="reference external" href="http://tools.ietf.org/html/rfc2047.html"><strong>RFC 2047</strong></a> encoded lines.</dd></dl> <p>The <a title="email.header.Header" class="reference internal" href="#email.header.Header"><tt class="xref docutils literal"><span class="pre">Header</span></tt></a> class also provides a number of methods to support standard operators and built-in functions.</p> <dl class="method"> <dt id="email.header.Header.__str__"> <tt class="descname">__str__</tt><big>(</big><big>)</big><a class="headerlink" href="#email.header.Header.__str__" title="Permalink to this definition">¶</a></dt> <dd>A synonym for <a title="email.header.Header.encode" class="reference internal" href="#email.header.Header.encode"><tt class="xref docutils literal"><span class="pre">Header.encode()</span></tt></a>. Useful for <tt class="docutils literal"><span class="pre">str(aHeader)</span></tt>.</dd></dl> <dl class="method"> <dt id="email.header.Header.__unicode__"> <tt class="descname">__unicode__</tt><big>(</big><big>)</big><a class="headerlink" href="#email.header.Header.__unicode__" title="Permalink to this definition">¶</a></dt> <dd>A helper for the built-in <a title="unicode" class="reference external" href="functions.html#unicode"><tt class="xref docutils literal"><span class="pre">unicode()</span></tt></a> function. Returns the header as a Unicode string.</dd></dl> <dl class="method"> <dt id="email.header.Header.__eq__"> <tt class="descname">__eq__</tt><big>(</big><em>other</em><big>)</big><a class="headerlink" href="#email.header.Header.__eq__" title="Permalink to this definition">¶</a></dt> <dd>This method allows you to compare two <a title="email.header.Header" class="reference internal" href="#email.header.Header"><tt class="xref docutils literal"><span class="pre">Header</span></tt></a> instances for equality.</dd></dl> <dl class="method"> <dt id="email.header.Header.__ne__"> <tt class="descname">__ne__</tt><big>(</big><em>other</em><big>)</big><a class="headerlink" href="#email.header.Header.__ne__" title="Permalink to this definition">¶</a></dt> <dd>This method allows you to compare two <a title="email.header.Header" class="reference internal" href="#email.header.Header"><tt class="xref docutils literal"><span class="pre">Header</span></tt></a> instances for inequality.</dd></dl> </dd></dl> <p>The <tt class="xref docutils literal"><span class="pre">email.header</span></tt> module also provides the following convenient functions.</p> <dl class="function"> <dt id="email.header.decode_header"> <tt class="descclassname">email.header.</tt><tt class="descname">decode_header</tt><big>(</big><em>header</em><big>)</big><a class="headerlink" href="#email.header.decode_header" title="Permalink to this definition">¶</a></dt> <dd><p>Decode a message header value without converting the character set. The header value is in <em>header</em>.</p> <p>This function returns a list of <tt class="docutils literal"><span class="pre">(decoded_string,</span> <span class="pre">charset)</span></tt> pairs containing each of the decoded parts of the header. <em>charset</em> is <tt class="xref docutils literal"><span class="pre">None</span></tt> for non-encoded parts of the header, otherwise a lower case string containing the name of the character set specified in the encoded string.</p> <p>Here’s an example:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">email.header</span> <span class="kn">import</span> <span class="n">decode_header</span> <span class="gp">>>> </span><span class="n">decode_header</span><span class="p">(</span><span class="s">'=?iso-8859-1?q?p=F6stal?='</span><span class="p">)</span> <span class="go">[('p\xf6stal', 'iso-8859-1')]</span> </pre></div> </div> </dd></dl> <dl class="function"> <dt id="email.header.make_header"> <tt class="descclassname">email.header.</tt><tt class="descname">make_header</tt><big>(</big><em>decoded_seq</em><span class="optional">[</span>, <em>maxlinelen</em><span class="optional">[</span>, <em>header_name</em><span class="optional">[</span>, <em>continuation_ws</em><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><big>)</big><a class="headerlink" href="#email.header.make_header" title="Permalink to this definition">¶</a></dt> <dd><p>Create a <a title="email.header.Header" class="reference internal" href="#email.header.Header"><tt class="xref docutils literal"><span class="pre">Header</span></tt></a> instance from a sequence of pairs as returned by <a title="email.header.decode_header" class="reference internal" href="#email.header.decode_header"><tt class="xref docutils literal"><span class="pre">decode_header()</span></tt></a>.</p> <p><a title="email.header.decode_header" class="reference internal" href="#email.header.decode_header"><tt class="xref docutils literal"><span class="pre">decode_header()</span></tt></a> takes a header value string and returns a sequence of pairs of the format <tt class="docutils literal"><span class="pre">(decoded_string,</span> <span class="pre">charset)</span></tt> where <em>charset</em> is the name of the character set.</p> <p>This function takes one of those sequence of pairs and returns a <a title="email.header.Header" class="reference internal" href="#email.header.Header"><tt class="xref docutils literal"><span class="pre">Header</span></tt></a> instance. Optional <em>maxlinelen</em>, <em>header_name</em>, and <em>continuation_ws</em> are as in the <a title="email.header.Header" class="reference internal" href="#email.header.Header"><tt class="xref docutils literal"><span class="pre">Header</span></tt></a> constructor.</p> </dd></dl> </div> </div> </div> </div> <div class="sphinxsidebar"> <div class="sphinxsidebarwrapper"> <h4>Previous topic</h4> <p class="topless"><a href="email.mime.html" title="previous chapter">18.1.4. <tt class="docutils literal docutils literal"><span class="pre">email</span></tt>: Creating email and MIME objects from scratch</a></p> <h4>Next topic</h4> <p class="topless"><a href="email.charset.html" title="next chapter">18.1.6. <tt class="docutils literal docutils literal docutils literal"><span class="pre">email</span></tt>: Representing character sets</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/email.header.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="../modindex.html" title="Global Module Index" >modules</a> |</li> <li class="right" > <a href="email.charset.html" title="18.1.6. email: Representing character sets" >next</a> |</li> <li class="right" > <a href="email.mime.html" title="18.1.4. email: Creating email and MIME objects from scratch" >previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="../index.html">Python v2.6.6 documentation</a> »</li> <li><a href="index.html" >The Python Standard Library</a> »</li> <li><a href="netdata.html" >18. 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