title: SQLalchemy race timer to numeric conversion
body: <p>I am selecting data of alpine skiing race times from a SQL database table to be used for analysis using SQLalchemy Core in python. One of the columns, timetot, in my table, result, represents a timer value stored as a string. An example of a timetot string is "1:53.54" (minutes:seconds.milliseconds) that I want to convert to a float 113.54 (seconds). <br>
  I am currently converting this timer string to a numeric with this very cumbersome piece of code:</p>
  
  <pre><code>from sqlalchemy import Select, cast, func, Numeric
  
  stmt = select([cast(func.substring(result.c.timetot, 1,1), 
  Numeric)*60 + cast(func.substring(result.c.timetot, 3,9), 
  Numeric(6,2))])
  </code></pre>
  
  <p>I have two questions:<br><br>
  1. Does anyone have a nicer (i.e. more compact) way of performing this conversion? <br><br>
  2. I have two more columns in the table to perform the same conversion on, is it possible to define a function somehow with SQLalchemy to avoid repeating the code?</p>
  
  <p><br></p>
  
  <p>I'm using SQLAlchemy version 1.1.13 and Python 3.6.3</p>
  
  <p><br>
  Thanks!</p>