Python判断一个文件夹内哪些文件是图片的实例

def is_img(ext):
 ext = ext.lower()
 if ext == '.jpg':
  return True
 elif ext == '.png':
  return True
 elif ext == '.jpeg':
  return True
 elif ext == '.bmp':
  return True
 else:
  return False

for x in os.listdir(directory):
 if is_img(osp.splitext(x)[1]):
  do something