title: UnboundLocalError: local variable 'a' referenced before assignment
body: <p>if execute the following code will show error message:</p>
  
  <p><strong>UnboundLocalError: local variable 'a' referenced before assignment</strong></p>
  
  <pre><code>a = 220.0
  b = 4300.0
  c = 230.0/4300.0
  
  def fun():
      while (c &gt; a/b):
          a = a + 1
          print a/b
  
  if __name__ == '__main__':
      fun()
  </code></pre>
  
  <p>but modify to :</p>
  
  <pre><code>a = 220.0
  b = 4300.0
  c = 230.0/4300.0
  
  def fun():
      aa = a
      bb = b
      while (c &gt; aa/bb):
          aa = aa + 1
          print aa/bb
  
  if __name__ == '__main__':
      fun()
  </code></pre>
  
  <p>it will fine.
  Any advice or pointers would be awesome. Thanks a lot!</p>