试用python3.7 + Django2.1.3的时候, 在创建模型类关联外键时, 报如下错误: Traceback (most recent call last): xxxxxxxxxxx TypeError: __init__() missing 1 required positional argument: 'on_delete' 解决办法: # 关联外键时设置`on_delete=`参数即可 student_grade = models.ForeignKey('Grades', on_delete=models.CASCADE)