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<div class="section" id="tailoring-atexit-hooks">
<h1>Tailoring <cite>atexit</cite> hooks<a class="headerlink" href="#tailoring-atexit-hooks" title="Permalink to this headline">¶</a></h1>
<p>In some situations you may want to tailor the typical messages that PyTables
outputs:</p>
<div class="highlight-python"><pre>Closing remaining open files: /tmp/prova.h5... done</pre>
</div>
<p>The responsible of this behaviour is the <tt class="xref py py-meth docutils literal"><span class="pre">tables.file.close_open_files()</span></tt>
function that is being registered via <tt class="xref py py-func docutils literal"><span class="pre">atexit.register()</span></tt> Python function.
Although you can’t de-register already registered cleanup functions, you can
register new ones to tailor the existing behaviour.
For example, if you register this function:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="k">def</span> <span class="nf">my_close_open_files</span><span class="p">(</span><span class="n">verbose</span><span class="p">):</span>
<span class="n">open_files</span> <span class="o">=</span> <span class="n">tb</span><span class="o">.</span><span class="n">file</span><span class="o">.</span><span class="n">_open_files</span>
<span class="n">are_open_files</span> <span class="o">=</span> <span class="nb">len</span><span class="p">(</span><span class="n">open_files</span><span class="p">)</span> <span class="o">></span> <span class="mi">0</span>
<span class="k">if</span> <span class="n">verbose</span> <span class="ow">and</span> <span class="n">are_open_files</span><span class="p">:</span>
<span class="k">print</span> <span class="o">>></span> <span class="n">sys</span><span class="o">.</span><span class="n">stderr</span><span class="p">,</span> <span class="s">"Closing remaining open files:"</span><span class="p">,</span>
<span class="k">for</span> <span class="n">fileh</span> <span class="ow">in</span> <span class="n">open_files</span><span class="o">.</span><span class="n">keys</span><span class="p">():</span>
<span class="k">if</span> <span class="n">verbose</span><span class="p">:</span>
<span class="k">print</span> <span class="o">>></span> <span class="n">sys</span><span class="o">.</span><span class="n">stderr</span><span class="p">,</span> <span class="s">"</span><span class="si">%s</span><span class="s">..."</span> <span class="o">%</span> <span class="p">(</span><span class="n">open_files</span><span class="p">[</span><span class="n">fileh</span><span class="p">]</span><span class="o">.</span><span class="n">filename</span><span class="p">,),</span>
<span class="n">open_files</span><span class="p">[</span><span class="n">fileh</span><span class="p">]</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
<span class="k">if</span> <span class="n">verbose</span><span class="p">:</span>
<span class="k">print</span> <span class="o">>></span> <span class="n">sys</span><span class="o">.</span><span class="n">stderr</span><span class="p">,</span> <span class="s">"done"</span><span class="p">,</span>
<span class="k">if</span> <span class="n">verbose</span> <span class="ow">and</span> <span class="n">are_open_files</span><span class="p">:</span>
<span class="k">print</span> <span class="o">>></span> <span class="n">sys</span><span class="o">.</span><span class="n">stderr</span>
<span class="kn">import</span> <span class="nn">sys</span><span class="o">,</span> <span class="nn">atexit</span>
<span class="n">atexit</span><span class="o">.</span><span class="n">register</span><span class="p">(</span><span class="n">my_close_open_files</span><span class="p">,</span> <span class="bp">False</span><span class="p">)</span>
</pre></div>
</div>
<p>then, you won’t get the closing messages anymore because the new registered
function is executed before the existing one.
If you want the messages back again, just set the verbose parameter to true.</p>
<p>You can also use the <cite>atexit</cite> hooks to perform other cleanup functions as well.</p>
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