title: Applying Conditions on Pandas DataFrame Columns before reading csv or tsv files
body: <p>Is it possible to set conditions (filters) for the DataFrame columns before reading a csv or tsv files, If I am already aware of the column names and types? If yes, how?</p>
  
  <p>For Example: Consider there are two numerical columns (col1 and col2) in a very big file. I do not want to load whole file in the memory and select only those rows where col1 greater than col2. Therefore, first, I want to set the condition on the dataframe that it should read only those rows from the csv file where col1 is greater than col2. I hope my explanation make sense.</p>
  
  <p>Thanks  </p>