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<div class="section" id="spelling-module">
<h1><tt class="docutils literal"><span class="pre">spelling</span></tt> module<a class="headerlink" href="#spelling-module" title="Permalink to this headline">¶</a></h1>
<p>See <a class="reference internal" href="../spelling.html"><em>correcting errors in user queries</em></a>.</p>
<span class="target" id="module-whoosh.spelling"></span><p>This module contains helper functions for correcting typos in user queries.</p>
<div class="section" id="corrector-objects">
<h2>Corrector objects<a class="headerlink" href="#corrector-objects" title="Permalink to this headline">¶</a></h2>
<dl class="class">
<dt id="whoosh.spelling.Corrector">
<em class="property">class </em><tt class="descclassname">whoosh.spelling.</tt><tt class="descname">Corrector</tt><a class="headerlink" href="#whoosh.spelling.Corrector" title="Permalink to this definition">¶</a></dt>
<dd><p>Base class for spelling correction objects. Concrete sub-classes should
implement the <tt class="docutils literal"><span class="pre">_suggestions</span></tt> method.</p>
<dl class="method">
<dt id="whoosh.spelling.Corrector.suggest">
<tt class="descname">suggest</tt><big>(</big><em>text</em>, <em>limit=5</em>, <em>maxdist=2</em>, <em>prefix=0</em><big>)</big><a class="headerlink" href="#whoosh.spelling.Corrector.suggest" title="Permalink to this definition">¶</a></dt>
<dd><table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first last simple">
<li><strong>text</strong> – the text to check. This word will <strong>not</strong> be added to the
suggestions, even if it appears in the word graph.</li>
<li><strong>limit</strong> – only return up to this many suggestions. If there are not
enough terms in the field within <tt class="docutils literal"><span class="pre">maxdist</span></tt> of the given word, the
returned list will be shorter than this number.</li>
<li><strong>maxdist</strong> – the largest edit distance from the given word to look
at. Values higher than 2 are not very effective or efficient.</li>
<li><strong>prefix</strong> – require suggestions to share a prefix of this length
with the given word. This is often justifiable since most
misspellings do not involve the first letter of the word. Using a
prefix dramatically decreases the time it takes to generate the
list of words.</li>
</ul>
</td>
</tr>
</tbody>
</table>
</dd></dl>
</dd></dl>
<dl class="class">
<dt id="whoosh.spelling.ReaderCorrector">
<em class="property">class </em><tt class="descclassname">whoosh.spelling.</tt><tt class="descname">ReaderCorrector</tt><big>(</big><em>reader</em>, <em>fieldname</em><big>)</big><a class="headerlink" href="#whoosh.spelling.ReaderCorrector" title="Permalink to this definition">¶</a></dt>
<dd><p>Suggests corrections based on the content of a field in a reader.</p>
<p>Ranks suggestions by the edit distance, then by highest to lowest
frequency.</p>
</dd></dl>
<dl class="class">
<dt id="whoosh.spelling.GraphCorrector">
<em class="property">class </em><tt class="descclassname">whoosh.spelling.</tt><tt class="descname">GraphCorrector</tt><big>(</big><em>graph</em><big>)</big><a class="headerlink" href="#whoosh.spelling.GraphCorrector" title="Permalink to this definition">¶</a></dt>
<dd><p>Suggests corrections based on the content of a raw
<tt class="xref py py-class docutils literal"><span class="pre">whoosh.automata.fst.GraphReader</span></tt> object.</p>
<p>By default ranks suggestions based on the edit distance.</p>
</dd></dl>
<dl class="class">
<dt id="whoosh.spelling.MultiCorrector">
<em class="property">class </em><tt class="descclassname">whoosh.spelling.</tt><tt class="descname">MultiCorrector</tt><big>(</big><em>correctors</em><big>)</big><a class="headerlink" href="#whoosh.spelling.MultiCorrector" title="Permalink to this definition">¶</a></dt>
<dd><p>Merges suggestions from a list of sub-correctors.</p>
</dd></dl>
</div>
<div class="section" id="querycorrector-objects">
<h2>QueryCorrector objects<a class="headerlink" href="#querycorrector-objects" title="Permalink to this headline">¶</a></h2>
<dl class="class">
<dt id="whoosh.spelling.QueryCorrector">
<em class="property">class </em><tt class="descclassname">whoosh.spelling.</tt><tt class="descname">QueryCorrector</tt><a class="headerlink" href="#whoosh.spelling.QueryCorrector" title="Permalink to this definition">¶</a></dt>
<dd><p>Base class for objects that correct words in a user query.</p>
<dl class="method">
<dt id="whoosh.spelling.QueryCorrector.correct_query">
<tt class="descname">correct_query</tt><big>(</big><em>q</em>, <em>qstring</em><big>)</big><a class="headerlink" href="#whoosh.spelling.QueryCorrector.correct_query" title="Permalink to this definition">¶</a></dt>
<dd><p>Returns a <a class="reference internal" href="#whoosh.spelling.Correction" title="whoosh.spelling.Correction"><tt class="xref py py-class docutils literal"><span class="pre">Correction</span></tt></a> object representing the corrected
form of the given query.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
<li><strong>q</strong> – the original <a class="reference internal" href="query.html#whoosh.query.Query" title="whoosh.query.Query"><tt class="xref py py-class docutils literal"><span class="pre">whoosh.query.Query</span></tt></a> tree to be
corrected.</li>
<li><strong>qstring</strong> – the original user query. This may be None if the
original query string is not available, in which case the
<tt class="docutils literal"><span class="pre">Correction.string</span></tt> attribute will also be None.</li>
</ul>
</td>
</tr>
<tr class="field-even field"><th class="field-name">Return type:</th><td class="field-body"><p class="first last"><a class="reference internal" href="#whoosh.spelling.Correction" title="whoosh.spelling.Correction"><tt class="xref py py-class docutils literal"><span class="pre">Correction</span></tt></a></p>
</td>
</tr>
</tbody>
</table>
</dd></dl>
</dd></dl>
<dl class="class">
<dt id="whoosh.spelling.SimpleQueryCorrector">
<em class="property">class </em><tt class="descclassname">whoosh.spelling.</tt><tt class="descname">SimpleQueryCorrector</tt><big>(</big><em>correctors</em>, <em>terms</em>, <em>prefix=0</em>, <em>maxdist=2</em><big>)</big><a class="headerlink" href="#whoosh.spelling.SimpleQueryCorrector" title="Permalink to this definition">¶</a></dt>
<dd><p>A simple query corrector based on a mapping of field names to
<a class="reference internal" href="#whoosh.spelling.Corrector" title="whoosh.spelling.Corrector"><tt class="xref py py-class docutils literal"><span class="pre">Corrector</span></tt></a> objects, and a list of <tt class="docutils literal"><span class="pre">("fieldname",</span> <span class="pre">"text")</span></tt> tuples
to correct. And terms in the query that appear in list of term tuples are
corrected using the appropriate corrector.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first last simple">
<li><strong>correctors</strong> – a dictionary mapping field names to
<a class="reference internal" href="#whoosh.spelling.Corrector" title="whoosh.spelling.Corrector"><tt class="xref py py-class docutils literal"><span class="pre">Corrector</span></tt></a> objects.</li>
<li><strong>terms</strong> – a sequence of <tt class="docutils literal"><span class="pre">("fieldname",</span> <span class="pre">"text")</span></tt> tuples
representing terms to be corrected.</li>
<li><strong>prefix</strong> – suggested replacement words must share this number of
initial characters with the original word. Increasing this even to
just <tt class="docutils literal"><span class="pre">1</span></tt> can dramatically speed up suggestions, and may be
justifiable since spellling mistakes rarely involve the first
letter of a word.</li>
<li><strong>maxdist</strong> – the maximum number of “edits” (insertions, deletions,
subsitutions, or transpositions of letters) allowed between the
original word and any suggestion. Values higher than <tt class="docutils literal"><span class="pre">2</span></tt> may be
slow.</li>
</ul>
</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="class">
<dt id="whoosh.spelling.Correction">
<em class="property">class </em><tt class="descclassname">whoosh.spelling.</tt><tt class="descname">Correction</tt><big>(</big><em>q</em>, <em>qstring</em>, <em>corr_q</em>, <em>tokens</em><big>)</big><a class="headerlink" href="#whoosh.spelling.Correction" title="Permalink to this definition">¶</a></dt>
<dd><p>Represents the corrected version of a user query string. Has the
following attributes:</p>
<dl class="docutils">
<dt><tt class="docutils literal"><span class="pre">query</span></tt></dt>
<dd>The corrected <a class="reference internal" href="query.html#whoosh.query.Query" title="whoosh.query.Query"><tt class="xref py py-class docutils literal"><span class="pre">whoosh.query.Query</span></tt></a> object.</dd>
<dt><tt class="docutils literal"><span class="pre">string</span></tt></dt>
<dd>The corrected user query string.</dd>
<dt><tt class="docutils literal"><span class="pre">original_query</span></tt></dt>
<dd>The original <a class="reference internal" href="query.html#whoosh.query.Query" title="whoosh.query.Query"><tt class="xref py py-class docutils literal"><span class="pre">whoosh.query.Query</span></tt></a> object that was corrected.</dd>
<dt><tt class="docutils literal"><span class="pre">original_string</span></tt></dt>
<dd>The original user query string.</dd>
<dt><tt class="docutils literal"><span class="pre">tokens</span></tt></dt>
<dd>A list of token objects representing the corrected words.</dd>
</dl>
<p>You can also use the <tt class="xref py py-meth docutils literal"><span class="pre">Correction.format_string()</span></tt> to reformat the
corrected query string using a <tt class="xref py py-class docutils literal"><span class="pre">whoosh.highlight.Formatter</span></tt> class.
For example, to display the corrected query string as HTML with the
changed words emphasized:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">whoosh</span> <span class="kn">import</span> <span class="n">highlight</span>
<span class="n">correction</span> <span class="o">=</span> <span class="n">mysearcher</span><span class="o">.</span><span class="n">correct_query</span><span class="p">(</span><span class="n">q</span><span class="p">,</span> <span class="n">qstring</span><span class="p">)</span>
<span class="n">hf</span> <span class="o">=</span> <span class="n">highlight</span><span class="o">.</span><span class="n">HtmlFormatter</span><span class="p">(</span><span class="n">classname</span><span class="o">=</span><span class="s">"change"</span><span class="p">)</span>
<span class="n">html</span> <span class="o">=</span> <span class="n">correction</span><span class="o">.</span><span class="n">format_string</span><span class="p">(</span><span class="n">hf</span><span class="p">)</span>
</pre></div>
</div>
</dd></dl>
</div>
</div>
</div>
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<h3><a href="../index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#"><tt class="docutils literal"><span class="pre">spelling</span></tt> module</a><ul>
<li><a class="reference internal" href="#corrector-objects">Corrector objects</a></li>
<li><a class="reference internal" href="#querycorrector-objects">QueryCorrector objects</a></li>
</ul>
</li>
</ul>
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<h4>Next topic</h4>
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