title: How to force pandas read_csv to use float32 for all float columns?
body: <p>Because</p>
  
  <ul>
  <li>I don't need double precision</li>
  <li>My machine has limited memory and I want to process bigger datasets</li>
  <li>I need to pass the extracted data (as matrix) to BLAS libraries, and BLAS calls for single precision are 2x faster than for double precision equivalence.</li>
  </ul>
  
  <p>Note that not all columns in the raw csv file have float types. I only need to set float32 as the default for float columns.</p>