title: python-tesseract OCR: get digits only
body: <p>I'm using tesseract OCRwith python-tesseract.
  In the <a href="http://code.google.com/p/tesseract-ocr/wiki/FAQ">tesseract FAQ</a>, regarding digits, we have:</p>
  
  <blockquote>
    <p>Use</p>
    
    <p><code>TessBaseAPI::SetVariable("tessedit_char_whitelist", "0123456789");</code></p>
    
    <p>BEFORE calling an Init function or put this in a text file called
    tessdata/configs/digits:</p>
    
    <p><code>tessedit_char_whitelist 0123456789</code></p>
    
    <p>and then your command line becomes:</p>
    
    <p><code>tesseract image.tif outputbase nobatch digits</code></p>
    
    <p>Warning: Until the old and new config variables get merged, you must
    have the nobatch parameter too.</p>
  </blockquote>
  
  <p>In python-tesseract, the SetVariable method exists. I've tried this, but the result of the OCR is the same:</p>
  
  <pre><code>api = tesseract.TessBaseAPI()
  api.SetVariable("tessedit_char_whitelist", "0123456789")
  api.Init('.','eng',tesseract.OEM_DEFAULT)
  api.SetPageSegMode(tesseract.PSM_AUTO)
  </code></pre>
  
  <p>Did anyone already got this working, or should I consider it a bug in python-tesseract?</p>