title: Tab Error in Python
body: <p>The following python code throws this error message, and I can't tell why, my tabs seem to be in line: </p>
  
  <pre><code>File "test.py", line 12
      pass
         ^ TabError: inconsistent use of tabs and spaces in indentation
  </code></pre>
  
  <p>My code:</p>
  
  <pre><code>class eightPuzzle(StateSpace):
      StateSpace.n = 0
  
      def __init__(self, action, gval, state, parent = None):
          StateSpace.__init__(self, action, gval, parent)
          self.state = state
  
      def successors(self) :
          pass
  </code></pre>