title: applying a string function to a pandas dataframe column
body: <p>this seems somewhat basic but after going through stackoverflow I couldn't seem to take everything answered and solve my problem.  so i'm working on my text processing skills.  I put car reviews in a pandas dataframe looking like this:</p>
  
  <pre><code>    Review
  0   :P I like you, Merc. You make me laugh! If Mat...
  1   I am surprised that I did not find any discuss...
  3   . . .let me see if I am following along correc...
  4   . . .now hold on a minute. A "current" A6 4.2 ...
  5   but has anyone noticed the front oh the new ac...
  </code></pre>
  
  <p>i wrote a function that takes a string as input and returns a value (in my case a sentiment score).  within my function, this value will be put in a newly created column.  the problem I obviously keep coming across is with the input - i get an expected string error.  with a dataframe, there are objects not strings. </p>
  
  <p>the function is very long and works when a string is inputed.  here's a snippet of the function:  note that dataframe is titled edmunds.</p>
  
  <pre><code>def checker(b):
      word = 'ls'
      if stry.find(word) == -1:
          edmunds['ls'] = 0.0
      ...
      edmunds['ls'] = sum(o_list)
  </code></pre>
  
  <p>any help would be greatly appreciated.  trying to wrap my head around if i should go from dataframe to list or if i could still work within pandas.</p>
  
  <p>output would ideally look like:</p>
  
  <pre><code>Review                                                 ls
  0   :P I like you, Merc. You make me laugh! If Mat...  0.4
  1   I am surprised that I did not find any discuss...  0.5
  3   . . .let me see if I am following along correc...  0.0
  4   . . .now hold on a minute. A "current" A6 4.2 ...  1.0
  5   but has anyone noticed the front oh the new ac...  -0.6
  </code></pre>