title: Python can't find 'main' module
body: <p>When I run the code using the command <code>python filename.py</code>, I am getting the following error,</p>
  
  <p><code>/Library/anaconda/bin/python: can't find '__main__' module in filename.py</code></p>
  
  <p>I am not sure what exactly is going wrong here. I need help correcting this.
  How can I correct this?</p>
  
  <pre><code>SUFFIXES = {1000: ['KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'],
              1024: ['KiB', 'MiB', 'GiB', 'TiB', 'PiB', 'EiB', 'ZiB', 'YiB']}
  
  def approximate_size(size, a_kilobyte_is_1024_bytes=True):
      '''Convert a file size to human-readable form.
  
      Keyword arguments:
      size -- file size in bytes
      a_kilobyte_is_1024_bytes -- if True (default), use multiples of 1024
                                  if False, use multiples of 1000
  
      Returns: string
  
      '''
      if size &lt; 0:
          raise ValueError('number must be non-negative')
  
      multiple = 1024 if a_kilobyte_is_1024_bytes else 1000
      for suffix in SUFFIXES[multiple]:
          size /= multiple
          if size &lt; multiple:
              return '{0:.1f} {1}'.format(size, suffix)
  
      raise ValueError('number too large')
  
  if __name__ == “__main__”:
      print(“Hello World”)
      print(approximate_size(1000000000000, False))
      print(approximate_size(1000000000000))
  </code></pre>