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.

def getserialnum(flist):
    """
    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.
    """
    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