django 对models中上传的文件或图片改名

def user_directory_path(instance,filename):
    print instance,filename
    ext = filename.split('.')[-1]
    print 'ext',ext
    filename = '{}.{}'.format(uuid.uuid4().hex[:10], ext)
    print filename
    # print os.path.join(instance.user.id, "avatar", filename)
    return os.path.join("uepload", filename)

class Course(models.Model):
    detail = UEditorField(verbose_name="课程详情",width=600, height=300, imagePath="courses/",filePath="courses/", default='')
    is_banner = models.BooleanField(default=False, verbose_name="是否轮播")
    degree = models.CharField(verbose_name="难度", choices=(("cj","初级"), ("zj","中级"), ("gj","高级")), max_length=2)
    fav_nums = models.IntegerField(default=0, verbose_name='收藏人数')
    image = models.ImageField(upload_to=user_directory_path, verbose_name="封面图", max_length=100)
    click_nums = models.IntegerField(default=0, verbose_name="点击数")

　　class Meta:
    　　verbose_name = "课程"
    　　erbose_name_plural = verbose_name

定义一个函数，在函数中使用uuid.uuid4().hex[:10]，生成一个10位随机数，返回给model类