title: python converting map to list taking a long time
body: <p><strong>EDIT</strong>: I'm using Python 3.5.0, and so <code>map()</code> will return an iterator instead of a <code>list</code>, unlike Python 2.x</p>
  
  <p>I have a list of units and I am calling a REST api on all of them to return more data about them. I'm using <code>map()</code> to do this, but when I try to convert that map to a list, the program hangs there and doesn't proceed (both when I run it and debug it)</p>
  
  <pre><code>data = list(map(lambda product: client.request(units_url + "/" + product), units))
  </code></pre>
  
  <p>At first I thought maybe it was an issue with calling the api so quickly, but when I iterate through the map (without converting it to a list) manually and print it goes just fine:</p>
  
  <pre><code>data = map(lambda product: client.request(units_url + "/" + product), units)
  for item in data:
      print(item)    # &lt;-- this works just fine for the entire map
  </code></pre>
  
  <p>Anyone know why I'm getting this behavior? </p>