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<span id="reg-gotchas"></span><h1>Gotchas<a class="headerlink" href="#gotchas" title="Permalink to this headline">ΒΆ</a></h1>
<p>PyWavelets utilizes <tt class="docutils literal"><span class="pre">NumPy</span></tt> under the hood. That’s why handling the data
containing <tt class="xref docutils literal"><span class="pre">None</span></tt> values can be surprising. <tt class="xref docutils literal"><span class="pre">None</span></tt> values are converted to
‘not a number’ (<tt class="docutils literal"><span class="pre">numpy.NaN</span></tt>) values:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">numpy</span><span class="o">,</span> <span class="nn">pywt</span>
<span class="gp">>>> </span><span class="n">x</span> <span class="o">=</span> <span class="p">[</span><span class="bp">None</span><span class="p">,</span> <span class="bp">None</span><span class="p">]</span>
<span class="gp">>>> </span><span class="n">mode</span> <span class="o">=</span> <span class="s">'sym'</span>
<span class="gp">>>> </span><span class="n">wavelet</span> <span class="o">=</span> <span class="s">'db1'</span>
<span class="gp">>>> </span><span class="n">cA</span><span class="p">,</span> <span class="n">cD</span> <span class="o">=</span> <span class="n">pywt</span><span class="o">.</span><span class="n">dwt</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">wavelet</span><span class="p">,</span> <span class="n">mode</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">numpy</span><span class="o">.</span><span class="n">all</span><span class="p">(</span><span class="n">numpy</span><span class="o">.</span><span class="n">isnan</span><span class="p">(</span><span class="n">cA</span><span class="p">))</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="n">numpy</span><span class="o">.</span><span class="n">all</span><span class="p">(</span><span class="n">numpy</span><span class="o">.</span><span class="n">isnan</span><span class="p">(</span><span class="n">cD</span><span class="p">))</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="n">rec</span> <span class="o">=</span> <span class="n">pywt</span><span class="o">.</span><span class="n">idwt</span><span class="p">(</span><span class="n">cA</span><span class="p">,</span> <span class="n">cD</span><span class="p">,</span> <span class="n">wavelet</span><span class="p">,</span> <span class="n">mode</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">numpy</span><span class="o">.</span><span class="n">all</span><span class="p">(</span><span class="n">numpy</span><span class="o">.</span><span class="n">isnan</span><span class="p">(</span><span class="n">rec</span><span class="p">))</span>
<span class="go">True</span>
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