title: Multiple dependent widgets (dropdown menu) on Jupyter notebook
body: <p>I was following the example on how to handle multiple dependent widgets on jupyter notebooks from here:</p>
  
  <p><a href="https://stackoverflow.com/questions/28529157/dynamically-changing-dropdowns-in-ipython-notebook-widgets-and-spyre/29333253">Dynamically changing dropdowns in IPython notebook widgets and Spyre</a></p>
  
  <p>In that example the code solution was the following:</p>
  
  <pre><code>from IPython.html import widgets
  from IPython.display import display
  
  geo={'USA':['CHI','NYC'],'Russia':['MOW','LED']}
  
  def print_city(city):
      print city
  
  def select_city(country):
      cityW.options = geo[country]
  
  
  scW = widgets.Dropdown(options=geo.keys())
  init = scW.value
  cityW = widgets.Dropdown(options=geo[init])
  j = widgets.interactive(print_city, city=cityW)
  i = widgets.interactive(select_city, country=scW)
  display(i)
  display(j)
  </code></pre>
  
  <p>so, the second dropdown is dependent on the value of the first one.
  Here the question: <strong>What if i want to create a third dropdown that is dependent on the value of the second one?</strong> Let's say that each of the cities above (CHI, NYC, MOW, LED) have some districts, and I'd like a third dropdown that change every time that a city is updated.</p>
  
  <p>Hope that the problem is clear, thank you!</p>