new_contents: # doc-export: UsingPython
  """
  This example demonstrates what things from Python land can be used in JS.
  
  Flexx detects what names are used in the transpiled JS of a Model (or
  Widget class, and tries to look these up in the module, converting the
  used objects if possible.
  
  Check out the source of the generated page to see what Flexx did.
  
  Note that once running, there is no interaction with the Python side, so this
  example be exported to standalone HTML.
  """
  
  from flexx import event, app, ui
  
  # Define a value. This can be used in JS as long as it can be serialized
  # using JSON (None, bool, int, float, str, list, dict).
  # The definition of this value is inside the JS version of this module.
  info = dict(name='John', age=42)
  
  # Import a value from another module. It's still just a value, and there is
  # no way for Flexx to tell where it was defined, so on the JS side it is
  # defined in *this* module just like info. This means that if you import
  # and use a value in different modules, in JS these are different instances.
  from sys import version
  
  # Define a function (or a class). Provided that its compatible with PyScript,
  # you can just use this in the JS. Note that if this function used a value
  # or a function, that would be converted too.
  def poly(x, *coefs):
      degree = len(coefs) - 1
      y = 0
      for coef in coefs:
          y += coef * x ** degree
          degree -= 1
      return y
  
  # Import a (PyScript-compatible) function from another module. In this case
  # Flexx can tell where it was defined and put it in its own module. See
  # the page source.
  from html import escape
  
  
  class UsingPython(ui.Widget):
      
      def init(self):
          self.label = ui.Label(wrap=0)
      
      class JS:
          
          def init(self):
              # A rather boring way to present the info. The point is that
              # we're using all sorts of Python stuff here, that is automatically
              # converted for us.
              lines = []
              lines.append('This JS was generated from Python ' + version)
              lines.append('Person %s is %i years old' % (info.name, info.age))
              lines.append('Evaling 4*x**2 + 5*x + 6 with x=4: ' + poly(4, 4, 5, 6))
              lines.append('... and with x=12: ' + poly(12, 4, 5, 6))
              lines.append('String with escaped html: ' + escape('html <tags>!'))
              lines.append('String with escaped html: ' + escape('Woezel & Pip'))
              
              self.label.text = '<br />'.join(lines)
  
  
  if __name__ == '__main__':
      m = app.launch(UsingPython, 'firefox')
      app.run()
  
subject: Add example for using Python in JS