title: Matplotlib Legend for Scatter with custom colours
body: <p>I'm a bit of newbie at this and am trying to create a scatter chart with custom bubble sizes and colours.  The chart displays fine but how do I get a legend saying what the colours refer to.  This is as far as I've got:</p>
  
  <pre><code>inc = []
  out = []
  bal = []
  col = []
  
  fig=Figure()
  ax=fig.add_subplot(111)
  
  inc = (30000,20000,70000)
  out = (80000,30000,40000)
  bal = (12000,10000,6000)
  col = (1,2,3)
  leg = ('proj1','proj2','proj3')
  
  ax.scatter(inc, out, s=bal, c=col)
  ax.axis([0, 100000, 0, 100000])
  
  ax.set_xlabel('income', fontsize=20)
  ax.set_ylabel('Expenditure', fontsize=20)
  ax.set_title('Project FInancial Positions %s' % dt)
  ax.grid(True)
  canvas=FigureCanvas(fig)
  response=HttpResponse(content_type='image/png')
  canvas.print_png(response)
  </code></pre>
  
  <p>This thread was helpful, but couldn't get it to solve my problem: <a href="https://stackoverflow.com/questions/872397/matplotlib-legend-not-displayed-properly">Matplotlib: Legend not displayed properly</a></p>