django迁移模型entry 提示 on delete

suishoufang

根据图书《python编程从入门到实践》来操作，修改完models.py后，执行命令python manage.py makemigrations learning_logs，就报错，求大神指点。


model.py 代码如下

from django.db import models
class Topic(models.Model):

"""用户学习的主题"""
text = models.CharField(max_length = 200)
date_added = models.DateTimeField(auto_now_add = True)

def __str__ (self):
    """返回模型的字符串表示"""
    return self.text
class Entry(models.Model):

"""学到的有关某个主题的具体知识"""
topic = models.ForeignKey(Topic)
text = models.TextField()
date_added = models.DateTimeField(auto_now_add = True)

class Meta:
    verbose_name_plural = 'entries'

def __str__(self):
    """返回模型的字符串表示"""
    return self.text[:50] + "..."


manage.py 代码如下

#!/usr/bin/env python
import os
import sys

if name == "__main__":

os.environ.setdefault("DJANGO_SETTINGS_MODULE", "learning_log.settings")
try:
    from django.core.management import execute_from_command_line
except ImportError as exc:
    raise ImportError(
        "Couldn't import Django. Are you sure it's installed and "
        "available on your PYTHONPATH environment variable? Did you "
        "forget to activate a virtual environment?"
    ) from exc
execute_from_command_line(sys.argv)

黑夜

  在迁移模型Entry时，运行代码python manage.py makemigrations learning_logs，报错

TypeError: __init__() missing 1 required positional argument: 'on_delete'

        经官方文档解释：https://docs.djangoproject.com/e ... /fields/#foreignkey发现foreignkey需要增加一个参数on_delete，于是将topic = models.ForeignKey(Topic)  更改为

topic = models.ForeignKey('Topic', on_delete=models.CASCADE)，成功运行。


来源 ：  https://blog.csdn.net/zhouyl02/article/details/79325748

suishoufang

黑夜 发表于 2018-4-4 10:21
在迁移模型Entry时，运行代码python manage.py makemigrations learning_logs，报错

TypeError: __ini ...

已解决，谢谢您

titanss

最近也在学习，Python和django更新太快了，跟不上节奏啊