改变了Django模型。我为DateField提供了一次性default = datetime.date。发现它无效。删除了该字段仍然无法迁移

Question

嗨，这是我在models.py中添加的具体行

billingMonth2 = models.DateTimeField()

这就是makemigrations中发生的事情，我想我添加了一个不可为空的字段，所以我尝试定义一个默认值：

    You are trying to add a non-nullable field 'billingMonth' to bills 
    without a default; we can't do that (the database needs something to populate
    existing rows).
    Please select a fix:
    1) Provide a one-off default now (will be set on all existing rows)
    2) Quit, and let me add a default in models.py
    Select an option: 1
    Please enter the default value now, as valid Python
    The datetime and django.utils.timezone modules are available, so you can do 
    e.g. timezone.now()
    >>> datetime.date
    Migrations for 'bills':
    0007_auto_20160609_1400.py:
    - Change Meta options on bills
    - Add field billingMonth to bills

我发现datetime.date无效并出现错误

    ....File "/home/jrbenriquez/Envs/env1/local/lib/python2.7/site-packages/django/db/backends/base/schema.py", line 197, in effective_default
default = field.get_default()
    File "/home/jrbenriquez/Envs/env1/local/lib/python2.7/site-packages/django/db/models/fields/__init__.py", line 797, in get_default
return self.default()
    TypeError: Required argument 'year' (pos 1) not found

所以我刚刚删除了billingMonth2字段，希望它恢复正常并将默认值设置为

    `billingMonth2 = models.DateTimeField(default='Test',null=True,blank=True)`

两者仍然给出相同的错误。在我看来，我已经在某个其他文件或数据库中的模型元中更改了某些内容，并且我必须在某处删除默认值“datetime.date”

我希望有人能在这里帮助我。谢谢！

更新：这是0007_auto20160609_1400.py

    # -*- coding: utf-8 -*-
    # Generated by Django 1.9.6 on 2016-06-09 14:00
    from __future__ import unicode_literals

    from django.db import migrations, models
    import django.utils.datetime_safe


    class Migration(migrations.Migration): 

        dependencies = [
            ('bills', '0006_bills_duedate'),
        ]

        operations = [
            migrations.AlterModelOptions(
                name='bills',
                options={'ordering': ('-id', '-status'),     'verbose_name_plural': 'Bills'},
             ),
            migrations.AddField(
                model_name='bills',
                name='billingMonth',
                field=models.DateField(default=django.utils.datetime_safe.date),
                preserve_default=False,
             ),
]

Answer 1

Please enter the default value now, as valid Python
The datetime and django.utils.timezone modules are available, so you can do e.g. timezone.now()
>>> datetime.date

我想这是要求方法的返回值，而不是方法本身。所以它的datetime.date()与()结束。

此外，在模型的字段声明中，您可以将当前日期设置为默认值，如果这是您尝试执行的操作

billingMonth2 = models.DateTimeField(default=datetime.date, null=True, blank=True)

你给它的方法本身，没有()，所以创建一个新行时，不仅在首次定义模型时。

Answer 2

在Makemigrations期间，使用：datetime.date.today（）用于填充数据库，否则您将获得“TypeError：function missing required required'year'（pos 1）”。