exiv2_process = subprocess.Popen(
    ["exiv2", "-PEkt", "-g",
     "-g", "Exif.Photo.LensModel",
     "-g", "Exif.NikonLd2.LensIDNumber", "-g", "Exif.NikonLd3.LensIDNumber", "-g", "Exif.Nikon3.Lens",
     "-g", "Exif.CanonCs.LensType", "-g", "Exif.Canon.LensModel"]
    + raw_file_group, stdout=subprocess.PIPE)

...


for line in lines:
    # Sometimes, values have trailing rubbish
    line = line.partition(b"\x00")[0].decode("utf-8")
    if "Exif.Photo." in line:
        filepath, data = line.split("Exif.Photo.")
    elif "Exif.Image." in line:
        filepath, data = line.split("Exif.Image.")
    elif "Exif.NikonLd2." in line:
        filepath, data = line.split("Exif.NikonLd2.")
    elif "Exif.NikonLd3." in line:
        filepath, data = line.split("Exif.NikonLd3.")
    elif "Exif.Nikon3." in line:
        filepath, data = line.split("Exif.Nikon3.")
    elif "Exif.CanonCs." in line:
        filepath, data = line.split("Exif.CanonCs.")
    elif "Exif.Canon." in line:
        filepath, data = line.split("Exif.Canon.")

...


    if fieldname in ["LensIDNumber", "LensType", "LensModel", "Lens"]:
        if (not exif_data[2] or len(field_value) > len(exif_data[2])) \
        and not invalid_lens_model_name_pattern.match(field_value):
            exif_data[2] = field_value