title: how to randomly choose multiple keys and its value in a dictionary python
body: <p>I have a dictionary like this:</p>
  
  <pre><code>user_dict = {
              user1: [(video1, 10),(video2,20),(video3,1)]
              user2: [(video1, 4),(video2,8),(video6,45)]
              ...
              user100: [(video1, 46),(video2,34),(video6,4)]                 
              } 
  
  (video1,10) means (videoid, number of request)
  </code></pre>
  
  <p>Now I want to randomly choose 10 users and do some calculation like </p>
  
  <pre><code> 1. calculate number of videoid for each user. 
   2. sum up the number of requests for these 10 random users, etc
  </code></pre>
  
  <p>then I need to increase the random number to 20, 30, 40 respectively</p>
  
  <p>But "random.choice" can only choose one value at a time, right? how to choose multiple keys and the list following each key?</p>