python3.7使用models.ForeignKey时一定要传入实参on_delete=models.CASCADE

 1 from django.db import models
 2 
 3 class Musician(models.Model):
 4     first_name = models.CharField(max_length=50)
 5     last_name = models.CharField(max_length=50)
 6     instrument = models.CharField(max_length=100)
 7 
 8 #使用models.ForeignKey时python3.7一定要传入实参on_delete=models.CASCADE
 9 class Album(models.Model):
10     artist = models.ForeignKey(Musician, on_delete=models.CASCADE)
11     name = models.CharField(max_length=100)
12     release_date = models.DateField()
13     num_stars = models.IntegerField()