django - Django错误:关键字参数有多个值

Question

在使用重写的构造函数实例化Django表单时，出现以下错误:

__init__() got multiple values for keyword argument 'collection_type'

__init__()函数(如下所示)与此完全相同，但是 # code用我的逻辑替换了。除此之外，我实质上是重写表单的(是ModelForm)构造函数。

def __init__(self, collection_type, user=None, parent=None, *args, **kwargs):
    # code
    super(self.__class__, self).__init__(*args, **kwargs)

产生错误的调用如下所示:

form = CreateCollectionForm(
    request.POST, 
    collection_type=collection_type, 
    parent=parent, 
    user=request.user
)

我看不到错误 pop 的任何原因。

编辑:这是构造函数的完整代码

def __init__(self, collection_type, user=None, parent=None, *args, **kwargs):
    self.collection_type = collection_type
    if self.collection_type == 'library':
        self.user = user
    elif self.collection_type == 'bookshelf' or self.collection_type == 'series':
        self.parent = parent
    else:
        raise AssertionError, 'collection_type must be "library", "bookshelf" or "series"'
    super(self.__class__, self).__init__(*args, **kwargs)

编辑:Stacktrace

Environment:

Request Method: POST
Request URL: http://localhost:8000/forms/create_bookshelf/hello
Django Version: 1.1.1
Python Version: 2.6.1
Installed Applications:
['django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.sites',
 'libraries',
 'users',
 'books',
 'django.contrib.admin',
 'googlehooks',
 'registration']
Installed Middleware:
('django.middleware.common.CommonMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware')


Traceback:
File "/Library/Python/2.6/site-packages/django/core/handlers/base.py" in get_response
  92.                 response = callback(request, *callback_args, **callback_kwargs)
File "/Library/Python/2.6/site-packages/django/contrib/auth/decorators.py" in __call__
  78.             return self.view_func(request, *args, **kwargs)
File "/Users/marcus/Sites/marcuswhybrow.net/autolib/libraries/forms.py" in     create_collection
  13.           form = CreateCollectionForm(request.POST,     collection_type=collection_type, user=request.user)

Exception Type: TypeError at /forms/create_bookshelf/hello
Exception Value: __init__() got multiple values for keyword argument 'collection_type'

Answer 1

您将collection_type参数作为关键字参数传递，因为您在对表单构造函数的调用中特别说了collection_type=collection_type。因此，Python将其包含在kwargs字典中-但是由于您也已将其声明为该函数定义中的位置参数，因此它尝试将其传递两次，从而导致错误。

但是，您尝试执行的操作将永远无法进行。您不能在user=None, parent=None字典之前使用*args，因为它们已经是kwargs了，而args必须始终在kwargs之前。解决此问题的方法是删除collection_type，user和parent的显式定义，并从函数中的kwargs中提取它们:

def __init__(self, *args, **kwargs):
    collection_type = kwargs.pop('collection_type', None)
    user = kwargs.pop('user', None)
    parent = kwargs.pop('parent', None)