title: float' object has no attribute 'lower'
body: <p>I'm facing this error and I'm really not able to find the reason for it.<br>
  Can somebody please point out the reason for it ?</p>
  
  <pre><code>for i in tweet_raw.comments:
      mns_proc.append(processComUni(i))
  
  ---------------------------------------------------------------------------
  AttributeError                            Traceback (most recent call last)
  &lt;ipython-input-416-439073b420d1&gt; in &lt;module&gt;()
        1 for i in tweet_raw.comments:
  ----&gt; 2     tweet_processed.append(processtwt(i))
        3 
  
  &lt;ipython-input-414-4e1b8a8fb285&gt; in processtwt(tweet)
        4     #Convert to lower case
        5     #tweet = re.sub('RT[\s]+','',tweet)
  ----&gt; 6     tweet = tweet.lower()
        7     #Convert www.* or https?://* to URL
        8     #tweet = re.sub('((www\.[\s]+)|(https?://[^\s]+))','',tweet)
  
  AttributeError: 'float' object has no attribute 'lower'
  </code></pre>
  
  <p>A second similar error that facing is this :</p>
  
  <pre><code>for i in tweet_raw.comments:
      tweet_proc.append(processtwt(i))
  
  ---------------------------------------------------------------------------
  TypeError                                 Traceback (most recent call last)
  &lt;ipython-input-423-439073b420d1&gt; in &lt;module&gt;()
        1 for i in tweet_raw.comments:
  ----&gt; 2     tweet_proc.append(processtwt(i))
        3 
  
  &lt;ipython-input-421-38fab2ef704e&gt; in processComUni(tweet)
       11         tweet=re.sub(('[http]+s?://[^\s&lt;&gt;"]+|www\.[^\s&lt;&gt;"]+'),'', tweet)
       12     #Convert @username to AT_USER
  ---&gt; 13     tweet = re.sub('@[^\s]+',' ',tweet)
       14     #Remove additional white spaces
       15     tweet = re.sub('[\s]+', ' ', tweet)
  
  C:\Users\m1027201\AppData\Local\Continuum\Anaconda\lib\re.pyc in sub(pattern, repl, string, count, flags)
      149     a callable, it's passed the match object and must return
      150     a replacement string to be used."""
  --&gt; 151     return _compile(pattern, flags).sub(repl, string, count)
      152 
      153 def subn(pattern, repl, string, count=0, flags=0):
  
  TypeError: expected string or buffer
  </code></pre>
  
  <p>Shall I check whether of not a particluar tweet is tring before passing it to processtwt() function ? For this error I dont even know which line its failing at.</p>