title: Merge CSVs in Python with different columns
body: <p>I have hundreds of large CSV files that I would like to merge into one. However, not all CSV files contain all columns. Therefore, I need to merge files based on column name, not column position.</p>
  
  <p>Just to be clear: in the merged CSV, values should be empty for a cell coming from a line which did not have the column of that cell.</p>
  
  <p>I cannot use the pandas module, because it makes me run out of memory.</p>
  
  <p>Is there a module that can do that, or some easy code?</p>