title: Apply Custom Function and write to CSV every N rows
body: <p>I have a large dataframe and am trying to apply a custom function to one of the columns. However, as the function is a GET request to a website, it is rather slow, and the apply function breaks after an hour or so.</p>
  <p>As such, my current thinking is to break the dataframe up into subsamples of N rows each, apply the custom function, and appending the results to a csv. I'd like to know the most ideal way to perform this, especially on the portion of iterating N rows and saving to csv every N rows.</p>
  <p>Thanks in advance!</p>