title: Python regular expression match multiple words anywhere
body: <p>I'm trying to use python's regular expression to match a string with several words.
  For example, the string is "These are oranges and apples and pears, but not pinapples or .." The list of words I want to find is 'and', 'or' and 'not'. No matter the order or the position.</p>
  
  <p>I tried <code>r'AND | OR | NOT</code> 
  but didn't work.</p>
  
  <p>Also tried <code>r'.*?\bAND\b.*?\bOR\b.*?\bNOT\b.*?$</code>
  still didn't work...</p>
  
  <p>Not good at regular expression.. 
  And hint?
  Thanks!</p>