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<div class="section" id="module-xdrlib">
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<span id="xdrlib-encode-and-decode-xdr-data"></span><h1>13.5. <a class="reference internal" href="#module-xdrlib" title="xdrlib: Encoders and decoders for the External Data Representation (XDR)."><code class="xref py py-mod docutils literal"><span class="pre">xdrlib</span></code></a> — Encode and decode XDR data<a class="headerlink" href="#module-xdrlib" title="Permalink to this headline">¶</a></h1>
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<p id="index-0"><strong>Source code:</strong> <a class="reference external" href="https://hg.python.org/cpython/file/2.7/Lib/xdrlib.py">Lib/xdrlib.py</a></p>
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<hr class="docutils" />
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<p>The <a class="reference internal" href="#module-xdrlib" title="xdrlib: Encoders and decoders for the External Data Representation (XDR)."><code class="xref py py-mod docutils literal"><span class="pre">xdrlib</span></code></a> module supports the External Data Representation Standard as
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described in <span class="target" id="index-1"></span><a class="rfc reference external" href="https://tools.ietf.org/html/rfc1014.html"><strong>RFC 1014</strong></a>, written by Sun Microsystems, Inc. June 1987. It
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supports most of the data types described in the RFC.</p>
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<p>The <a class="reference internal" href="#module-xdrlib" title="xdrlib: Encoders and decoders for the External Data Representation (XDR)."><code class="xref py py-mod docutils literal"><span class="pre">xdrlib</span></code></a> module defines two classes, one for packing variables into XDR
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representation, and another for unpacking from XDR representation. There are
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also two exception classes.</p>
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<dt id="xdrlib.Packer">
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<em class="property">class </em><code class="descclassname">xdrlib.</code><code class="descname">Packer</code><a class="headerlink" href="#xdrlib.Packer" title="Permalink to this definition">¶</a></dt>
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<dd><p><a class="reference internal" href="#xdrlib.Packer" title="xdrlib.Packer"><code class="xref py py-class docutils literal"><span class="pre">Packer</span></code></a> is the class for packing data into XDR representation. The
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<a class="reference internal" href="#xdrlib.Packer" title="xdrlib.Packer"><code class="xref py py-class docutils literal"><span class="pre">Packer</span></code></a> class is instantiated with no arguments.</p>
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<dt id="xdrlib.Unpacker">
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<em class="property">class </em><code class="descclassname">xdrlib.</code><code class="descname">Unpacker</code><span class="sig-paren">(</span><em>data</em><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Unpacker" title="Permalink to this definition">¶</a></dt>
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<dd><p><code class="docutils literal"><span class="pre">Unpacker</span></code> is the complementary class which unpacks XDR data values from a
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string buffer. The input buffer is given as <em>data</em>.</p>
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<div class="admonition seealso">
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<p class="first admonition-title">See also</p>
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<dl class="last docutils">
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<dt><span class="target" id="index-2"></span><a class="rfc reference external" href="https://tools.ietf.org/html/rfc1014.html"><strong>RFC 1014</strong></a> - XDR: External Data Representation Standard</dt>
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<dd>This RFC defined the encoding of data which was XDR at the time this module was
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originally written. It has apparently been obsoleted by <span class="target" id="index-3"></span><a class="rfc reference external" href="https://tools.ietf.org/html/rfc1832.html"><strong>RFC 1832</strong></a>.</dd>
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<dt><span class="target" id="index-4"></span><a class="rfc reference external" href="https://tools.ietf.org/html/rfc1832.html"><strong>RFC 1832</strong></a> - XDR: External Data Representation Standard</dt>
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<dd>Newer RFC that provides a revised definition of XDR.</dd>
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<div class="section" id="packer-objects">
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<span id="xdr-packer-objects"></span><h2>13.5.1. Packer Objects<a class="headerlink" href="#packer-objects" title="Permalink to this headline">¶</a></h2>
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<p><a class="reference internal" href="#xdrlib.Packer" title="xdrlib.Packer"><code class="xref py py-class docutils literal"><span class="pre">Packer</span></code></a> instances have the following methods:</p>
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<dt id="xdrlib.Packer.get_buffer">
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<code class="descclassname">Packer.</code><code class="descname">get_buffer</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Packer.get_buffer" title="Permalink to this definition">¶</a></dt>
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<dd><p>Returns the current pack buffer as a string.</p>
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<dt id="xdrlib.Packer.reset">
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<code class="descclassname">Packer.</code><code class="descname">reset</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Packer.reset" title="Permalink to this definition">¶</a></dt>
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<dd><p>Resets the pack buffer to the empty string.</p>
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<p>In general, you can pack any of the most common XDR data types by calling the
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appropriate <code class="docutils literal"><span class="pre">pack_type()</span></code> method. Each method takes a single argument, the
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value to pack. The following simple data type packing methods are supported:
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<code class="xref py py-meth docutils literal"><span class="pre">pack_uint()</span></code>, <code class="xref py py-meth docutils literal"><span class="pre">pack_int()</span></code>, <code class="xref py py-meth docutils literal"><span class="pre">pack_enum()</span></code>, <code class="xref py py-meth docutils literal"><span class="pre">pack_bool()</span></code>,
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<code class="xref py py-meth docutils literal"><span class="pre">pack_uhyper()</span></code>, and <code class="xref py py-meth docutils literal"><span class="pre">pack_hyper()</span></code>.</p>
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<dt id="xdrlib.Packer.pack_float">
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<code class="descclassname">Packer.</code><code class="descname">pack_float</code><span class="sig-paren">(</span><em>value</em><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Packer.pack_float" title="Permalink to this definition">¶</a></dt>
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<dd><p>Packs the single-precision floating point number <em>value</em>.</p>
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<dt id="xdrlib.Packer.pack_double">
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<code class="descclassname">Packer.</code><code class="descname">pack_double</code><span class="sig-paren">(</span><em>value</em><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Packer.pack_double" title="Permalink to this definition">¶</a></dt>
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<dd><p>Packs the double-precision floating point number <em>value</em>.</p>
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<p>The following methods support packing strings, bytes, and opaque data:</p>
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<dt id="xdrlib.Packer.pack_fstring">
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<code class="descclassname">Packer.</code><code class="descname">pack_fstring</code><span class="sig-paren">(</span><em>n</em>, <em>s</em><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Packer.pack_fstring" title="Permalink to this definition">¶</a></dt>
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<dd><p>Packs a fixed length string, <em>s</em>. <em>n</em> is the length of the string but it is
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<em>not</em> packed into the data buffer. The string is padded with null bytes if
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necessary to guaranteed 4 byte alignment.</p>
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<dt id="xdrlib.Packer.pack_fopaque">
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<code class="descclassname">Packer.</code><code class="descname">pack_fopaque</code><span class="sig-paren">(</span><em>n</em>, <em>data</em><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Packer.pack_fopaque" title="Permalink to this definition">¶</a></dt>
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<dd><p>Packs a fixed length opaque data stream, similarly to <a class="reference internal" href="#xdrlib.Packer.pack_fstring" title="xdrlib.Packer.pack_fstring"><code class="xref py py-meth docutils literal"><span class="pre">pack_fstring()</span></code></a>.</p>
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<dt id="xdrlib.Packer.pack_string">
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<code class="descclassname">Packer.</code><code class="descname">pack_string</code><span class="sig-paren">(</span><em>s</em><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Packer.pack_string" title="Permalink to this definition">¶</a></dt>
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<dd><p>Packs a variable length string, <em>s</em>. The length of the string is first packed
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as an unsigned integer, then the string data is packed with
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<a class="reference internal" href="#xdrlib.Packer.pack_fstring" title="xdrlib.Packer.pack_fstring"><code class="xref py py-meth docutils literal"><span class="pre">pack_fstring()</span></code></a>.</p>
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<dt id="xdrlib.Packer.pack_opaque">
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<code class="descclassname">Packer.</code><code class="descname">pack_opaque</code><span class="sig-paren">(</span><em>data</em><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Packer.pack_opaque" title="Permalink to this definition">¶</a></dt>
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<dd><p>Packs a variable length opaque data string, similarly to <a class="reference internal" href="#xdrlib.Packer.pack_string" title="xdrlib.Packer.pack_string"><code class="xref py py-meth docutils literal"><span class="pre">pack_string()</span></code></a>.</p>
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<dt id="xdrlib.Packer.pack_bytes">
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<code class="descclassname">Packer.</code><code class="descname">pack_bytes</code><span class="sig-paren">(</span><em>bytes</em><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Packer.pack_bytes" title="Permalink to this definition">¶</a></dt>
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<dd><p>Packs a variable length byte stream, similarly to <a class="reference internal" href="#xdrlib.Packer.pack_string" title="xdrlib.Packer.pack_string"><code class="xref py py-meth docutils literal"><span class="pre">pack_string()</span></code></a>.</p>
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<p>The following methods support packing arrays and lists:</p>
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<dt id="xdrlib.Packer.pack_list">
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<code class="descclassname">Packer.</code><code class="descname">pack_list</code><span class="sig-paren">(</span><em>list</em>, <em>pack_item</em><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Packer.pack_list" title="Permalink to this definition">¶</a></dt>
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<dd><p>Packs a <em>list</em> of homogeneous items. This method is useful for lists with an
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indeterminate size; i.e. the size is not available until the entire list has
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been walked. For each item in the list, an unsigned integer <code class="docutils literal"><span class="pre">1</span></code> is packed
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first, followed by the data value from the list. <em>pack_item</em> is the function
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that is called to pack the individual item. At the end of the list, an unsigned
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integer <code class="docutils literal"><span class="pre">0</span></code> is packed.</p>
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<p>For example, to pack a list of integers, the code might appear like this:</p>
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<div class="highlight-python"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">xdrlib</span>
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<span class="n">p</span> <span class="o">=</span> <span class="n">xdrlib</span><span class="o">.</span><span class="n">Packer</span><span class="p">()</span>
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<span class="n">p</span><span class="o">.</span><span class="n">pack_list</span><span class="p">([</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">],</span> <span class="n">p</span><span class="o">.</span><span class="n">pack_int</span><span class="p">)</span>
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<dt id="xdrlib.Packer.pack_farray">
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<code class="descclassname">Packer.</code><code class="descname">pack_farray</code><span class="sig-paren">(</span><em>n</em>, <em>array</em>, <em>pack_item</em><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Packer.pack_farray" title="Permalink to this definition">¶</a></dt>
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<dd><p>Packs a fixed length list (<em>array</em>) of homogeneous items. <em>n</em> is the length of
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the list; it is <em>not</em> packed into the buffer, but a <a class="reference internal" href="exceptions.html#exceptions.ValueError" title="exceptions.ValueError"><code class="xref py py-exc docutils literal"><span class="pre">ValueError</span></code></a> exception
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is raised if <code class="docutils literal"><span class="pre">len(array)</span></code> is not equal to <em>n</em>. As above, <em>pack_item</em> is the
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function used to pack each element.</p>
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<dt id="xdrlib.Packer.pack_array">
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<code class="descclassname">Packer.</code><code class="descname">pack_array</code><span class="sig-paren">(</span><em>list</em>, <em>pack_item</em><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Packer.pack_array" title="Permalink to this definition">¶</a></dt>
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<dd><p>Packs a variable length <em>list</em> of homogeneous items. First, the length of the
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list is packed as an unsigned integer, then each element is packed as in
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<a class="reference internal" href="#xdrlib.Packer.pack_farray" title="xdrlib.Packer.pack_farray"><code class="xref py py-meth docutils literal"><span class="pre">pack_farray()</span></code></a> above.</p>
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<div class="section" id="unpacker-objects">
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<span id="xdr-unpacker-objects"></span><h2>13.5.2. Unpacker Objects<a class="headerlink" href="#unpacker-objects" title="Permalink to this headline">¶</a></h2>
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<p>The <a class="reference internal" href="#xdrlib.Unpacker" title="xdrlib.Unpacker"><code class="xref py py-class docutils literal"><span class="pre">Unpacker</span></code></a> class offers the following methods:</p>
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<dt id="xdrlib.Unpacker.reset">
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<code class="descclassname">Unpacker.</code><code class="descname">reset</code><span class="sig-paren">(</span><em>data</em><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Unpacker.reset" title="Permalink to this definition">¶</a></dt>
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<dd><p>Resets the string buffer with the given <em>data</em>.</p>
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<dt id="xdrlib.Unpacker.get_position">
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<code class="descclassname">Unpacker.</code><code class="descname">get_position</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Unpacker.get_position" title="Permalink to this definition">¶</a></dt>
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<dd><p>Returns the current unpack position in the data buffer.</p>
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<dt id="xdrlib.Unpacker.set_position">
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<code class="descclassname">Unpacker.</code><code class="descname">set_position</code><span class="sig-paren">(</span><em>position</em><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Unpacker.set_position" title="Permalink to this definition">¶</a></dt>
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<dd><p>Sets the data buffer unpack position to <em>position</em>. You should be careful about
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using <a class="reference internal" href="#xdrlib.Unpacker.get_position" title="xdrlib.Unpacker.get_position"><code class="xref py py-meth docutils literal"><span class="pre">get_position()</span></code></a> and <a class="reference internal" href="#xdrlib.Unpacker.set_position" title="xdrlib.Unpacker.set_position"><code class="xref py py-meth docutils literal"><span class="pre">set_position()</span></code></a>.</p>
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<dt id="xdrlib.Unpacker.get_buffer">
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<code class="descclassname">Unpacker.</code><code class="descname">get_buffer</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Unpacker.get_buffer" title="Permalink to this definition">¶</a></dt>
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<dd><p>Returns the current unpack data buffer as a string.</p>
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<dt id="xdrlib.Unpacker.done">
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<code class="descclassname">Unpacker.</code><code class="descname">done</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Unpacker.done" title="Permalink to this definition">¶</a></dt>
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<dd><p>Indicates unpack completion. Raises an <a class="reference internal" href="#xdrlib.Error" title="xdrlib.Error"><code class="xref py py-exc docutils literal"><span class="pre">Error</span></code></a> exception if all of the
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data has not been unpacked.</p>
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<p>In addition, every data type that can be packed with a <a class="reference internal" href="#xdrlib.Packer" title="xdrlib.Packer"><code class="xref py py-class docutils literal"><span class="pre">Packer</span></code></a>, can be
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unpacked with an <a class="reference internal" href="#xdrlib.Unpacker" title="xdrlib.Unpacker"><code class="xref py py-class docutils literal"><span class="pre">Unpacker</span></code></a>. Unpacking methods are of the form
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<code class="docutils literal"><span class="pre">unpack_type()</span></code>, and take no arguments. They return the unpacked object.</p>
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<dt id="xdrlib.Unpacker.unpack_float">
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<code class="descclassname">Unpacker.</code><code class="descname">unpack_float</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Unpacker.unpack_float" title="Permalink to this definition">¶</a></dt>
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<dd><p>Unpacks a single-precision floating point number.</p>
259
<dt id="xdrlib.Unpacker.unpack_double">
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<code class="descclassname">Unpacker.</code><code class="descname">unpack_double</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Unpacker.unpack_double" title="Permalink to this definition">¶</a></dt>
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<dd><p>Unpacks a double-precision floating point number, similarly to
262
<a class="reference internal" href="#xdrlib.Unpacker.unpack_float" title="xdrlib.Unpacker.unpack_float"><code class="xref py py-meth docutils literal"><span class="pre">unpack_float()</span></code></a>.</p>
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<p>In addition, the following methods unpack strings, bytes, and opaque data:</p>
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<dt id="xdrlib.Unpacker.unpack_fstring">
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<code class="descclassname">Unpacker.</code><code class="descname">unpack_fstring</code><span class="sig-paren">(</span><em>n</em><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Unpacker.unpack_fstring" title="Permalink to this definition">¶</a></dt>
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<dd><p>Unpacks and returns a fixed length string. <em>n</em> is the number of characters
270
expected. Padding with null bytes to guaranteed 4 byte alignment is assumed.</p>
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<dt id="xdrlib.Unpacker.unpack_fopaque">
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<code class="descclassname">Unpacker.</code><code class="descname">unpack_fopaque</code><span class="sig-paren">(</span><em>n</em><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Unpacker.unpack_fopaque" title="Permalink to this definition">¶</a></dt>
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<dd><p>Unpacks and returns a fixed length opaque data stream, similarly to
277
<a class="reference internal" href="#xdrlib.Unpacker.unpack_fstring" title="xdrlib.Unpacker.unpack_fstring"><code class="xref py py-meth docutils literal"><span class="pre">unpack_fstring()</span></code></a>.</p>
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<dt id="xdrlib.Unpacker.unpack_string">
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<code class="descclassname">Unpacker.</code><code class="descname">unpack_string</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Unpacker.unpack_string" title="Permalink to this definition">¶</a></dt>
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<dd><p>Unpacks and returns a variable length string. The length of the string is first
284
unpacked as an unsigned integer, then the string data is unpacked with
285
<a class="reference internal" href="#xdrlib.Unpacker.unpack_fstring" title="xdrlib.Unpacker.unpack_fstring"><code class="xref py py-meth docutils literal"><span class="pre">unpack_fstring()</span></code></a>.</p>
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<dt id="xdrlib.Unpacker.unpack_opaque">
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<code class="descclassname">Unpacker.</code><code class="descname">unpack_opaque</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Unpacker.unpack_opaque" title="Permalink to this definition">¶</a></dt>
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<dd><p>Unpacks and returns a variable length opaque data string, similarly to
292
<a class="reference internal" href="#xdrlib.Unpacker.unpack_string" title="xdrlib.Unpacker.unpack_string"><code class="xref py py-meth docutils literal"><span class="pre">unpack_string()</span></code></a>.</p>
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<dt id="xdrlib.Unpacker.unpack_bytes">
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<code class="descclassname">Unpacker.</code><code class="descname">unpack_bytes</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Unpacker.unpack_bytes" title="Permalink to this definition">¶</a></dt>
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<dd><p>Unpacks and returns a variable length byte stream, similarly to
299
<a class="reference internal" href="#xdrlib.Unpacker.unpack_string" title="xdrlib.Unpacker.unpack_string"><code class="xref py py-meth docutils literal"><span class="pre">unpack_string()</span></code></a>.</p>
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<p>The following methods support unpacking arrays and lists:</p>
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<dt id="xdrlib.Unpacker.unpack_list">
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<code class="descclassname">Unpacker.</code><code class="descname">unpack_list</code><span class="sig-paren">(</span><em>unpack_item</em><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Unpacker.unpack_list" title="Permalink to this definition">¶</a></dt>
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<dd><p>Unpacks and returns a list of homogeneous items. The list is unpacked one
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element at a time by first unpacking an unsigned integer flag. If the flag is
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<code class="docutils literal"><span class="pre">1</span></code>, then the item is unpacked and appended to the list. A flag of <code class="docutils literal"><span class="pre">0</span></code>
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indicates the end of the list. <em>unpack_item</em> is the function that is called to
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unpack the items.</p>
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<dt id="xdrlib.Unpacker.unpack_farray">
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<code class="descclassname">Unpacker.</code><code class="descname">unpack_farray</code><span class="sig-paren">(</span><em>n</em>, <em>unpack_item</em><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Unpacker.unpack_farray" title="Permalink to this definition">¶</a></dt>
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<dd><p>Unpacks and returns (as a list) a fixed length array of homogeneous items. <em>n</em>
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is number of list elements to expect in the buffer. As above, <em>unpack_item</em> is
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the function used to unpack each element.</p>
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<dt id="xdrlib.Unpacker.unpack_array">
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<code class="descclassname">Unpacker.</code><code class="descname">unpack_array</code><span class="sig-paren">(</span><em>unpack_item</em><span class="sig-paren">)</span><a class="headerlink" href="#xdrlib.Unpacker.unpack_array" title="Permalink to this definition">¶</a></dt>
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<dd><p>Unpacks and returns a variable length <em>list</em> of homogeneous items. First, the
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length of the list is unpacked as an unsigned integer, then each element is
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unpacked as in <a class="reference internal" href="#xdrlib.Unpacker.unpack_farray" title="xdrlib.Unpacker.unpack_farray"><code class="xref py py-meth docutils literal"><span class="pre">unpack_farray()</span></code></a> above.</p>
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<div class="section" id="exceptions">
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<span id="xdr-exceptions"></span><h2>13.5.3. Exceptions<a class="headerlink" href="#exceptions" title="Permalink to this headline">¶</a></h2>
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<p>Exceptions in this module are coded as class instances:</p>
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<dl class="exception">
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<dt id="xdrlib.Error">
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<em class="property">exception </em><code class="descclassname">xdrlib.</code><code class="descname">Error</code><a class="headerlink" href="#xdrlib.Error" title="Permalink to this definition">¶</a></dt>
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<dd><p>The base exception class. <a class="reference internal" href="#xdrlib.Error" title="xdrlib.Error"><code class="xref py py-exc docutils literal"><span class="pre">Error</span></code></a> has a single public attribute
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<code class="xref py py-attr docutils literal"><span class="pre">msg</span></code> containing the description of the error.</p>
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<dl class="exception">
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<dt id="xdrlib.ConversionError">
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<em class="property">exception </em><code class="descclassname">xdrlib.</code><code class="descname">ConversionError</code><a class="headerlink" href="#xdrlib.ConversionError" title="Permalink to this definition">¶</a></dt>
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<dd><p>Class derived from <a class="reference internal" href="#xdrlib.Error" title="xdrlib.Error"><code class="xref py py-exc docutils literal"><span class="pre">Error</span></code></a>. Contains no additional instance variables.</p>
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<p>Here is an example of how you would catch one of these exceptions:</p>
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<div class="highlight-python"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">xdrlib</span>
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<span class="n">p</span> <span class="o">=</span> <span class="n">xdrlib</span><span class="o">.</span><span class="n">Packer</span><span class="p">()</span>
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<span class="k">try</span><span class="p">:</span>
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<span class="n">p</span><span class="o">.</span><span class="n">pack_double</span><span class="p">(</span><span class="mf">8.01</span><span class="p">)</span>
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<span class="k">except</span> <span class="n">xdrlib</span><span class="o">.</span><span class="n">ConversionError</span> <span class="k">as</span> <span class="n">instance</span><span class="p">:</span>
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<span class="k">print</span> <span class="s1">'packing the double failed:'</span><span class="p">,</span> <span class="n">instance</span><span class="o">.</span><span class="n">msg</span>
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<h3><a href="../contents.html">Table Of Contents</a></h3>
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<li><a class="reference internal" href="#">13.5. <code class="docutils literal"><span class="pre">xdrlib</span></code> — Encode and decode XDR data</a><ul>
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<li><a class="reference internal" href="#packer-objects">13.5.1. Packer Objects</a></li>
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<li><a class="reference internal" href="#unpacker-objects">13.5.2. Unpacker Objects</a></li>
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<li><a class="reference internal" href="#exceptions">13.5.3. Exceptions</a></li>
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