title: Error with "argparse.ArgumentParser" in python
body: <p>This is giving a wierd error:</p>
  
  <pre><code>if __name__ == "__main__":
      import argparse
      import json
  
      from evaluation import cross_validation
      from predictor import PhraseSentimentPredictor
  
      parser = argparse.ArgumentParser(description=__doc__)
      parser.add_argument("filename")
      config = parser.parse_args()
      config = json.load(open(config.filename))
  </code></pre>
  
  <p>Error:</p>
  
  <blockquote>
  <pre><code>**usage: generate_kaggle_submission.py [-h] filename
      generate_kaggle_submission.py: error: too few arguments**
  </code></pre>
  </blockquote>
  
  <p>Please help</p>