title: Why dividing the value of column by other column create array in pandas? (I expected to get single value)
body: <p>I though that the operation I have was quite simple but got the result what I was not expecting. I have done following command for pandas dataframe and got array not single value. Can anyone tell me why and how to fix this?  </p>
  
  <pre><code>df["diff"] = (df["Total Facility"] / df["Total Facility_B"] - 1) * 100  
  </code></pre>
  
  <p><strong>Before</strong><br>
  <a href="https://i.stack.imgur.com/Bm1vz.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Bm1vz.jpg" alt="enter image description here"></a></p>
  
  <p><strong>After</strong><br>
  <a href="https://i.stack.imgur.com/TojKU.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/TojKU.png" alt="enter image description here"></a></p>
  
  <p><strong>Added</strong><br>
  When I apply following equation according to comment,</p>
  
  <pre><code>combined=(combined[["Total Facility", "Total Facility_B"]].applymap(type) == list).any()
  </code></pre>
  
  <p>I get following.</p>
  
  <pre><code>Total Facility  FALSE
  Total Facility_B    FALSE
  </code></pre>