title: in python, how do you denote required parameters and optional parameters in code?
body: <p>especially when there are so many parameters (10+ 20+).  </p>
  
  <p>What are good ways of enforcing <code>required/optional</code> parameters to a function?</p>
  
  <p>What are some good books that deal with this kind of questions for python?<br>
  (like effective c++ for c++)</p>
  
  <p>** EDIT **</p>
  
  <p>I think it's very unpractical to list <code>def foo(self, arg1, arg2, arg3,  .. arg20, .....):</code> when there are so many required parameters.</p>