 <p>Use <code>numpy.hstack()</code>:</p> <pre><code>&gt;&gt;&gt; import numpy &gt;&gt;&gt; desc = {'names': ('gender','age','weight'), 'formats': ('S1', 'f4', 'f4')} &gt;&gt;&gt; a = numpy.array([('M',64.0,75.0),('F',25.0,60.0)], dtype=desc) &gt;&gt;&gt; numpy.hstack((a,a)) array([('M', 64.0, 75.0), ('F', 25.0, 60.0), ('M', 64.0, 75.0), ('F', 25.0, 60.0)], dtype=[('gender', '|S1'), ('age', '&lt;f4'), ('weight', '&lt;f4')]) </code></pre>