title: python transitions lib - Wait for multiple events before transition from single state possible?
body: <p>Cross-post from github issue <a href="https://github.com/pytransitions/transitions/issues/247" rel="nofollow noreferrer">https://github.com/pytransitions/transitions/issues/247</a>.</p>
  
  <p>I'm using python's transitions FSM library and I need to wait for 3 things to happen before I transition to the next state.</p>
  
  <pre><code>State = WAIT_FOR_3_THINGS
  Events = thing_1_done, thing_2_done, thing_3_done
  </code></pre>
  
  <p>The thing_*_events can come in any order, so I'd prefer to avoid having a:</p>
  
  <p><code>thing_1_and_2_done</code>, <code>thing_1_and_3_done</code>, <code>thing_2_and_3_done</code> states</p>
  
  <p>I can track events, 1, 2, &amp; 3 and advance with a </p>
  
  <pre><code>conditions=[thing_1_and_2_done, thing_1_and_3_done, thing_2_and_3_done]
  </code></pre>
  
  <p>but I'm not sure where best to aggregate these event occurences.</p>
  
  <p>Is there a more skookum (ok, pythonic) way of doing this?</p>