code: def append_csv_data(file_strings):
      
      # Start with data from the first list element
      out_lines = list()
      head_line = None
  
      # Cycle through the lists of file strings, creating a list of line strings
      for fstrings in file_strings:
          file_lines = fstrings.split('\n')
  
          # Remove and save the header line
          head_line = file_lines.pop(0)
  
          # Save the data lines
          out_lines.extend(file_lines)
  
      # Sort the output lines by date and station (first two columns) in place
      out_lines.sort()
  
      # Remove all zero-length lines from front, add one to back, and add header
      i = 0
      while len(out_lines[i]) == 0:
          out_lines.pop(i)
  
      out_lines.insert(0, head_line)
      out_lines.append('')
  
      # Join the output lines into a single string
      out_string = "\n".join(out_lines)
  
      return out_string
docs: Append data from multiple csv files for the same time period
  
      Parameters
      -----------
      file_strings : array-like
          Lists or arrays of strings, where each string contains one file of data
  
      Returns
      -------
      out_string : string
          String with all data, ready for output to a file