title: matplotlibs ginput() with undefined number of points
body: <p>I need to define an area in a plot(s) using the matplotlib function ginput(). However since it is an irregular shape and will be different in each plot so I cant define how many points there will be before hand, i.e.</p>
  
  <pre><code>x = randn(10,10)
  imshow(x)
  n = I don't know yet
  points = ginput(n)
  </code></pre>
  
  <p>Anyone know how to go about this??
  thanks
  Dave</p>