title: Pandas to_csv() checking for overwrite
body: <p>When I am analyzing data, I save my dataframes into a csv-file and use <code>pd.to_csv()</code> for that. However, the function (over)writes the new file, without checking whether there exists one with the same name. <strong>Is there a way to check whether the file already exists, and if so, ask for a new filename?</strong></p>
  
  <p>I know I can add the system's datetime to the filename, which will prevent any overwriting, but I would like to know when I made the mistake. </p>