title: how to get the length of every element in one column
body: <p>In csv file, there is one column called "no_pun". There are some tokenized words in it. I want to get the length of every element in this column. This is easy in python. But I have an error.</p>
  
  <p>My code:</p>
  
  <pre><code>for i in range(0,len(data['no_pun'])):
      data["len_desc"][i] = len(data["no_pun"][i])
  </code></pre>
  
  <hr>
  
  <p>The KeyError:</p>
  
  <pre><code>  KeyError Traceback (most recent call last)
  /anaconda3/lib/python3.6/site-packages/pandas/core/indexes/base.py in get_loc(self, key, method, tolerance)
     2655             try:
  -&gt; 2656                 return self._engine.get_loc(key)
     2657             except KeyError:
  
  pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_loc()
  
  pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_loc()
  
  pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.PyObjectHashTable.get_item()
  
  pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.PyObjectHashTable.get_item()
  
  KeyError: 'len_desc'
  </code></pre>
  
  <p>During handling of the above exception, another exception occurred:</p>