title: python pandas: how to return an empty dataframe in a loop?
body: <p>to aggregate the content of a list of csv files , i normally do:</p>
  
  <pre><code>def getContent(fn):
      // do some thing with fn and generate a tempDataFrame
      return tempDataFrame
  
  
  agg = pd.concat([getContent(x) for x in myListOfFiles])
  </code></pre>
  
  <p>i feel this is a very neat solution.</p>
  
  <p>however, when something went wrong and i cannot find the fn or so, i need to return an empty tempDataFrame!</p>
  
  <p>How can i return an empty dataframe in this case? can anyone share some experiences?</p>
  
  <p>thanks!</p>