Django模型实例full_clean方法，对吗？

Question

我想要做的是编写代码，使我可以从csv文件中批量加载Django对象实例。 显然，在保存任何内容之前，我应该先检查所有数据。

tl; dr：full_clean（）方法无法捕获在没有null=True的字段中保存None的即将进行的尝试。 似乎是不正当的。 这是设计使然吗，为什么呢？ Django的错误比我以前使用过的其他错误少，所以“臭虫！” 似乎是最不可能的。

完整版本。 我认为行得通的是，为每一行创建一个对象实例，用电子表格中的数据填充字段，然后调用full_clean方法。 即（轮廓）

from django.core.exceptions import ValidationError
...

# upload a CSV file and open with a csvreader
errors=[]
for rownumber, row in enumerate(csvreader):

    o = SomeDjangoModel()
    o.somefield = row[0]  # repeated for all input data row[1] ...

    try:
        reason = ""
        o.full_clean()
    except ValidationError as e:
        reason = "Row:{} Reason:{}".format( rownumber, str(e))
        errors.append( reason)
        # reason, together with the row-number of the csv file, fully explains
        # what is wrong.

# end of loop
if errors:
    # display errors to the user for him to fix
else:
    # repeat the loop,  doing .save() instead of .full_clean() 
    # and get database integrity errors trying to save Null in non-null model field.

麻烦的是， .full_clean()不能在没有null=True字段中捕获None值

我该怎么办？ 想法包括

1. 将整个事务包装在事务中，在异常处理程序中执行一批o.save（），然后回滚整个事务，除非没有错误。 但是，当大概90％的尝试会以微不足道的方式出错时，为什么还要打扰数据库呢？

2. 即使没有与用户进行表单级别的每行交互，也可以通过表单输入数据。

3. 手动测试“无”应该不应该的位置。 但是.full_clean还能检查什么呢？

我可以理解，最终捕获数据库完整性错误的唯一方法是尝试存储数据，但是Django为什么不单独在null = False字段中捕获None？

顺便说一句，这是Django 1.9.6

添加了细节。 这是模型定义的相关领域

class OrderHistory( models.Model):
    invoice_no = models.CharField( max_length=10, unique=True)         # no default
    invoice_val= models.DecimalField( max_digits=8, decimal_places=2)  # no default
    date       = models.DateField( )                                   # no default

这就是发生在python manage.py shell事情，以证明.full_clean方法无法发现

>>> from orderhistory.models import OrderHistory
>>> from datetime import date
>>> o = OrderHistory( date=date(2010,3,17), invoice_no="21003163")
>>> o.invoice_val=None 
>>> o.full_clean()  # passes clean
>>> o.save() # attempt to save this one which has passed full_clean() validation
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/home/nigel/.virtualenvs/edge22/lib/python3.4/site-packages/django/db/models/base.py", line 708, in save
force_update=force_update, update_fields=update_fields)
  File "/home/nigel/.virtualenvs/edge22/lib/python3.4/site-packages/django/db/models/base.py", line 736, in save_base
    updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
  File "/home/nigel/.virtualenvs/edge22/lib/python3.4/site-packages/django/db/models/base.py", line 820, in _save_table
result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)
  File "/home/nigel/.virtualenvs/edge22/lib/python3.4/site-packages/django/db/models/base.py", line 859, in _do_insert
using=using, raw=raw)
  File "/home/nigel/.virtualenvs/edge22/lib/python3.4/site-packages/django/db/models/manager.py", line 122, in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/home/nigel/.virtualenvs/edge22/lib/python3.4/site-packages/django/db/models/query.py", line 1039, in _insert
return query.get_compiler(using=using).execute_sql(return_id)
  File "/home/nigel/.virtualenvs/edge22/lib/python3.4/site-packages/django/db/models/sql/compiler.py", line 1060, in execute_sql
cursor.execute(sql, params)
  File "/home/nigel/.virtualenvs/edge22/lib/python3.4/site-packages/django/db/backends/utils.py", line 79, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
  File "/home/nigel/.virtualenvs/edge22/lib/python3.4/site-packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
  File "/home/nigel/.virtualenvs/edge22/lib/python3.4/site-packages/django/db/utils.py", line 95, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/home/nigel/.virtualenvs/edge22/lib/python3.4/site-packages/django/utils/six.py", line 685, in reraise
raise value.with_traceback(tb)
  File "/home/nigel/.virtualenvs/edge22/lib/python3.4/site-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
django.db.utils.IntegrityError: null value in column "invoice_val" violates not-null constraint
DETAIL:  Failing row contains (2, 21003163, , , 2010-03-17, , null, null, null, null, null, null).
>>>
>>> p = OrderHistory( invoice_no="21003164") # no date
>>> p.date=None
>>> p.full_clean()                           # this DOES error as it should
  Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/home/nigel/.virtualenvs/edge22/lib/python3.4/site-packages/django/db/models/base.py", line 1144, in full_clean
  raise ValidationError(errors)
django.core.exceptions.ValidationError: {'date': ['This field cannot be null.']}
>>>

Answer 1

我刚刚在shell中重复了您的步骤，full_clean（）触发了None值的ValidationError：

>>> from orders.models import OrderHistory
>>> o = OrderHistory()
>>> o.full_clean()
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/Users/oz/.virtualenvs/full_clean_test/lib/python2.7/site-packages/django/db/models/base.py", line 1144, in full_clean
    raise ValidationError(errors)
ValidationError: {'date': [u'This field cannot be null.'], 'invoice_val': [u'This field cannot be null.'], 'invoice_no': [u'This field cannot be blank.']}

我已经在新项目中使用Django 1.9.6和Python 2.7.10在OSX上以及Python 3.4.3在Ubuntu上对它进行了测试。

尝试从项目中删除所有* .pyc文件。 如果那不起作用，请删除您的虚拟环境，创建一个新的环境并重新安装您的依赖项。