<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <title>Write your own filter — Pygments</title> <meta http-equiv="content-type" content="text/html; charset=utf-8"> <style type="text/css"> body { background-color: #f2f2f2; margin: 0; padding: 0; font-family: 'Georgia', serif; color: #111; } #content { background-color: white; padding: 20px; margin: 20px auto 20px auto; max-width: 800px; border: 4px solid #ddd; } h1 { font-weight: normal; font-size: 40px; color: #09839A; } h2 { font-weight: normal; font-size: 30px; color: #C73F00; } h1.heading { margin: 0 0 30px 0; } h2.subheading { margin: -30px 0 0 45px; } h3 { margin-top: 30px; } table.docutils { border-collapse: collapse; border: 2px solid #aaa; margin: 0.5em 1.5em 0.5em 1.5em; } table.docutils td { padding: 2px; border: 1px solid #ddd; } p, li, dd, dt, blockquote { font-size: 15px; color: #333; } p { line-height: 150%; margin-bottom: 0; margin-top: 10px; } hr { border-top: 1px solid #ccc; 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All you have to do is to subclass the <cite>Filter</cite> class and override the <cite>filter</cite> method. Additionally a filter is instanciated with some keyword arguments you can use to adjust the behavior of your filter.</p> <div class="section" id="subclassing-filters"> <h3>Subclassing Filters</h3> <p>As an example, we write a filter that converts all <cite>Name.Function</cite> tokens to normal <cite>Name</cite> tokens to make the output less colorful.</p> <div class="syntax"><pre><span class="kn">from</span> <span class="nn">pygments.util</span> <span class="kn">import</span> <span class="n">get_bool_opt</span> <span class="kn">from</span> <span class="nn">pygments.token</span> <span class="kn">import</span> <span class="n">Name</span> <span class="kn">from</span> <span class="nn">pygments.filter</span> <span class="kn">import</span> <span class="n">Filter</span> <span class="k">class</span> <span class="nc">UncolorFilter</span><span class="p">(</span><span class="n">Filter</span><span class="p">):</span> <span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="o">**</span><span class="n">options</span><span class="p">):</span> <span class="n">Filter</span><span class="o">.</span><span class="n">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="o">**</span><span class="n">options</span><span class="p">)</span> <span class="bp">self</span><span class="o">.</span><span class="n">class_too</span> <span class="o">=</span> <span class="n">get_bool_opt</span><span class="p">(</span><span class="n">options</span><span class="p">,</span> <span class="s">'classtoo'</span><span class="p">)</span> <span class="k">def</span> <span class="nf">filter</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">lexer</span><span class="p">,</span> <span class="n">stream</span><span class="p">):</span> <span class="k">for</span> <span class="n">ttype</span><span class="p">,</span> <span class="n">value</span> <span class="ow">in</span> <span class="n">stream</span><span class="p">:</span> <span class="k">if</span> <span class="n">ttype</span> <span class="ow">is</span> <span class="n">Name</span><span class="o">.</span><span class="n">Function</span> <span class="ow">or</span> <span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">class_too</span> <span class="ow">and</span> <span class="n">ttype</span> <span class="ow">is</span> <span class="n">Name</span><span class="o">.</span><span class="n">Class</span><span class="p">):</span> <span class="n">ttype</span> <span class="o">=</span> <span class="n">Name</span> <span class="k">yield</span> <span class="n">ttype</span><span class="p">,</span> <span class="n">value</span> </pre></div> <p>Some notes on the <cite>lexer</cite> argument: that can be quite confusing since it doesn't need to be a lexer instance. If a filter was added by using the <cite>add_filter()</cite> function of lexers, that lexer is registered for the filter. In that case <cite>lexer</cite> will refer to the lexer that has registered the filter. It <em>can</em> be used to access options passed to a lexer. Because it could be <cite>None</cite> you always have to check for that case if you access it.</p> </div> <div class="section" id="using-a-decorator"> <h3>Using a decorator</h3> <p>You can also use the <cite>simplefilter</cite> decorator from the <cite>pygments.filter</cite> module:</p> <div class="syntax"><pre><span class="kn">from</span> <span class="nn">pygments.util</span> <span class="kn">import</span> <span class="n">get_bool_opt</span> <span class="kn">from</span> <span class="nn">pygments.token</span> <span class="kn">import</span> <span class="n">Name</span> <span class="kn">from</span> <span class="nn">pygments.filter</span> <span class="kn">import</span> <span class="n">simplefilter</span> <span class="nd">@simplefilter</span> <span class="k">def</span> <span class="nf">uncolor</span><span class="p">(</span><span class="n">lexer</span><span class="p">,</span> <span class="n">stream</span><span class="p">,</span> <span class="n">options</span><span class="p">):</span> <span class="n">class_too</span> <span class="o">=</span> <span class="n">get_bool_opt</span><span class="p">(</span><span class="n">options</span><span class="p">,</span> <span class="s">'classtoo'</span><span class="p">)</span> <span class="k">for</span> <span class="n">ttype</span><span class="p">,</span> <span class="n">value</span> <span class="ow">in</span> <span class="n">stream</span><span class="p">:</span> <span class="k">if</span> <span class="n">ttype</span> <span class="ow">is</span> <span class="n">Name</span><span class="o">.</span><span class="n">Function</span> <span class="ow">or</span> <span class="p">(</span><span class="n">class_too</span> <span class="ow">and</span> <span class="n">ttype</span> <span class="ow">is</span> <span class="n">Name</span><span class="o">.</span><span class="n">Class</span><span class="p">):</span> <span class="n">ttype</span> <span class="o">=</span> <span class="n">Name</span> <span class="k">yield</span> <span class="n">ttype</span><span class="p">,</span> <span class="n">value</span> </pre></div> <p>The decorator automatically subclasses an internal filter class and uses the decorated function for filtering.</p> </div> </div> </body> <!-- generated on: 2010-03-01 21:18:23.568890 file id: filterdevelopment --> </html>