title: count unique rows in sql-alchemy
body: <p>I am new to sql alchemy and I would like to count unique rows in my table and output the unique rows together with the number of copies for that row. 
  Lets assume I have a table like this</p>
  
  <pre><code>Table A
  --------------
  id
  address
  </code></pre>
  
  <p>now I want to get all rows of this table but for rows with the same adress I want to get only one row (doesn't matter which id). I also want to know how many ids are at a particular address. 
  So if there are two people living at the same address "main street" (lets say id=4 and id =12) I would like to get an output like this ("main street", 2), </p>
  
  <p>Here is my starting attempt</p>
  
  <pre><code>query = models.A.query
  query = query.add_columns(func.count(models.A.address)).all()
  </code></pre>
  
  <p>this however, gives me the total number of rows in that table. So I guess func.count is the wrong function?
  thanks in advance
  carl</p>