title: Algorithm to find if location (latitude , longitude) is within radius range of a given location (latitude, longitude)
body: <p>I am given a file with interesting locations in some cities in the united states.</p>
  
  <p>in another file, I am given a lot of data for train/taxi pickups. I would like to know of an easy to implement algorithm to find if one of these pickup locations is within some <code>x</code> kilometers / miles from one of the interesting locations.</p>
  
  <p>I am writing a python script to do that.</p>
  
  <p><strong>EDIT</strong>
  I would like to know if I can import a library which has a function that I can use.</p>