如何在 Django 的 models.py 中创建数据库时修复迁移错误？答案

【问题标题】：How can I fix migrating error while creating a database in models.py in Django?如何在 Django 的 models.py 中创建数据库时修复迁移错误？
【发布时间】：2019-01-14 15:08:57
【问题描述】：

我已经开始使用无淀粉 Python Crash Course 学习 Django。在完成对“条目”进行编码的步骤时，我无法迁移数据库。显示错误。我正在使用 python 3.7 和 Django 2.0.7

我尝试过使用 python 3.6，但仍然无法正常工作

    Traceback (most recent call last):
  File "manage.py", line 15, in <module>
    execute_from_command_line(sys.argv)
  File "E:\Users\HCL\AppData\Local\Programs\Python\Python37\lib\site- 
 packages\django\core\management\__init__.py", line 371, in execute_from_command_line
    utility.execute()
  File "E:\Users\HCL\AppData\Local\Programs\Python\Python37\lib\site-packages\django\core\management\__init__.py", line 347, in execute
    django.setup()
  File "E:\Users\HCL\AppData\Local\Programs\Python\Python37\lib\site-packages\django\__init__.py", line 24, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "E:\Users\HCL\AppData\Local\Programs\Python\Python37\lib\site-packages\django\apps\registry.py", line 112, in populate
    app_config.import_models()
  File "E:\Users\HCL\AppData\Local\Programs\Python\Python37\lib\site-packages\django\apps\config.py", line 198, in import_models
    self.models_module = import_module(models_module_name)
  File "E:\Users\HCL\AppData\Local\Programs\Python\Python37\lib\importlib\__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1006, in _gcd_import
  File "<frozen importlib._bootstrap>", line 983, in _find_and_load
  File "<frozen importlib._bootstrap>", line 967, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 677, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 728, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "E:\Users\HCL\Desktop\learning_log\learning_logs\models.py", line 10, in <module>
    class Entry(models.Model):
  File "E:\Users\HCL\Desktop\learning_log\learning_logs\models.py", line 11, in Entry
    topic =  models.ForeignKey(Topic)
TypeError: __init__() missing 1 required positional argument: 'on_delete'

【问题讨论】：

您错过了 ForeignKey 上的 on_delete 参数。请阅读错误。
确保您使用的 django 版本与教程中使用的版本相同

标签： python django python-3.x django-models

【解决方案1】：

在您的模型中更改此行Entry

topic =  models.ForeignKey(Topic)

到

topic =  models.ForeignKey(Topic,on_delete=models.CASCADE)

【讨论】：