title: Streaming parquet file python and only downsampling
body: <p>I have data in parquet format which is too big to fit into memory (6 GB). I am looking for a way to read and process the file using Python 3.6. Is there a way to stream the file, down-sample, and save to a <code>dataframe</code>? Ultimately, I would like to have the data in <code>dataframe</code> format to work with.</p>
  
  <p>Am I wrong to attempt to do this without using a spark framework?</p>
  
  <p>I have tried using <code>pyarrow</code> and <code>fastparquet</code> but I get memory errors on trying to read the entire file in. 
  Any tips or suggestions would be greatly appreciated!</p>