title: ValueError: setting an array element with a sequence
body: <p>Why do the following code samples:</p>
  <pre><code>np.array([[1, 2], [2, 3, 4]])
  </code></pre>
  <pre><code>np.array([1.2, &quot;abc&quot;], dtype=float)
  </code></pre>
  <p>...all give the following error?</p>
  <blockquote>
  <p>ValueError: setting an array element with a sequence.</p>
  </blockquote>