title: Practical Python-based visual programming environment?
body: <p>I am looking for a practical visual programming environment based on Python.  My primary application is algorithm development for processing remote-sensing imagery.  I was initially inspired by LabVIEW from National Instruments, but that is more geared towards laboratory measurements and simulations.  I write a lot of prototype code in Python and do a lot of interactive analysis with IPython.</p>
  
  <p>Does there exist a visual framework where a "program" is represented by connected nodes which each read data, do some work, and output data to the next node?  I would like to use Python to write the code residing in each node.</p>
  
  <p>So far the best I've seen is Orange <a href="http://www.ailab.si/orange/" rel="nofollow noreferrer">http://www.ailab.si/orange/</a>, but it does not have the ability to start/stop individual nodes. </p>