title: Changing nested dictionary values in python
body: <p>I have a dictionary, who's keys are student ID #'s and the values are another dictionary. The nested dictionary has keys that state the type of assignment, and the values are the grades for the assignment, in a list.</p>
  
  <p>So I'm trying to change the list of grades for each assignment (to drop lowest grade, average them, etc.), but I can't figure out a way to pick them out of the dictionary in the first place. </p>
  
  <p>Here's what part of the dictionary looks like:</p>
  
  <pre><code>D = {"123-45-6789":{"hw":[98,89,92,75], "quiz":[45,36,42,50,29,27,40,41], "exam":[175,157]}, "534-77-9326":{"hw":[67,89,55,78], "quiz":[78,45,67,23,45,78,88,91], "exam":[187,146]},   ....... etc.
  </code></pre>
  
  <p>Any help will be very appreciated.</p>
  
  <p>***and I forgot to mention that I planned on iterating through the dictionary to edit each list of grades, because there are many student ID #'s. So I guess what I'm really asking is:
  What would the syntax look like to refer to each student ID #, then <em>each list of grades</em> for every ID #</p>