title: How to check for null elements in a list in a dataframe in np.where()?
body: <p>My dataframe, df:</p>
  <pre><code>Col_A Col_B
  Apple [1,2,3]
  Banana [1,null,4]
  Orange [6,null,null]
  </code></pre>
  <p>The nulls are represented as <code>np.nan</code>s in the dataframe. How can I check if all the values in each row of Col_B are null?<br />
  This is my <code>np.where</code>:</p>
  <pre><code>np.where(pd.isnull(df[Col_B]).all(), &quot;Fail&quot;, &quot;Pass&quot;)
  </code></pre>
  <p>However, I get a truth value is ambiguous even though I have a &quot;.all()&quot; there. Any way to get around this issue?</p>