title: Python stemmer issue: wrong stem
body: <p>Hi i'm trying to stem words with a python stemmer, i tried Porter and Lancaster, but they have the same problem. They can't stem correclty words that end with "er" or "e".</p>
  
  <p>for example, they stem</p>
  
  <pre><code>computer --&gt;  comput
  
  rotate   --&gt;  rotat
  </code></pre>
  
  <p>this is a part of the code</p>
  
  <pre><code>line=line.lower()
  line=re.sub(r'[^a-z0-9 ]',' ',line)
  line=line.split()
  line=[x for x in line if x not in stops]
  line=[ porter.stem(word, 0, len(word)-1) for word in line]
  # or 'line=[ st.stem(word) for word in line]'
  return line
  </code></pre>
  
  <p>any idea to fix this problem?</p>