code: def getserialnum(flist):
      
      sn = []
      for f in flist:
          tmp = search(r'(?<=CamSer)\d{3,6}', f)
          if tmp:
              ser = int(tmp.group())
          else:
              ser = None
          sn.append(ser)
      return sn
docs: This function assumes the serial number of the camera is in a particular place in the filename.
      Yes, this is a little lame, but it's how the original 2011 image-writing program worked, and I've
      carried over the scheme rather than appending bits to dozens of TB of files.