title: I can't understand polling/select in python
body: <p>I'm doing some threaded asynchronous networking experiment in python, using UDP.</p>
  
  <p>I'd like to understand polling and the select python module, I've never used them in C/C++.</p>
  
  <p>What are those for ? I kind of understand a little select, but does it block while watching a resource ? What is the purpose of polling ?</p>