title: Converting lists to dictionaries to check existence?
body: <p>If I instantiate/update a few lists very, very few times, in most cases only once, but I check for the existence of an object in that list a bunch of times, is it worth it to convert the lists into dictionaries and then check by key existence?</p>
  
  <p>Or in other words is it worth it for me to convert lists into dictionaries to achieve possible faster object existence checks?</p>