title: How to create a class (not a classifier) with a variable in IBM Watson Visual Recognition with Python?
body: <p>I'm trying to create a new class with the API like it's shown in the API Documentation <a href="https://cloud.ibm.com/apidocs/visual-recognition?code=python#update-a-classifier" rel="nofollow noreferrer">https://cloud.ibm.com/apidocs/visual-recognition?code=python#update-a-classifier</a></p>
  
  <p>The part that Watson uses as the name of the class is the prefix of "_positive_examples". I need to use the content of a variable as the prefix, but it's a keyword and I can't add any variable there (variableNotWorking in the code).</p>
  
  <p>I have tried to format as a string and also to create a dictionary in Python and introduce it there but I always obtain an error either from Python or Watson.</p>
  
  <pre><code>    positive = nuevaClase + '_positive_examples'
      visual_recognition = credencials()
      with open(aprDirFitxer1, 'rb') as nuevaClase:
              updated_model = visual_recognition.update_classifier(
                  classifier_id=classifId,
                  positive_examples={positive : nuevaClase}).get_result()
  </code></pre>
  
  <p>The error from Watson that I always obtain is:</p>
  
  <pre><code>watson_developer_cloud.watson_service.WatsonApiException: Error: Cannot execute learning task.  Did not find any files to process in the POST request body. , Code: 400 
  </code></pre>