AttributeError：“ tuple”对象在Django中没有属性“ get”

Question

I want to add a multiple choice field to my project app. This field should allow the user for select more than one choice. But I get an error. Before I added the multiple choice field, this part did not give any error. Where is my mistake?

my views.py

def project_new(request):
if request.method == 'POST':
    form = ProjectForm(request.POST)
    if form.is_valid():
        project = Project()
       ...
        project.lang_choices = form.cleaned_data['select_lang']
        project.save()
        return redirect('projects')
else:
    form = ProjectForm()


  return render(request, 'blog/project_new.html', {'form': form})

@login_required(login_url='/login/')
def project_details(request, pk):
    project = get_object_or_404(Project, pk=pk)
    return render(request, 'blog/project_detail.html', {'project': project})

my models.py

class ProgrammingLanguage(models.Model):
name = models.CharField(max_length=100)

def __str__(self):
    return self.name
class Project(models.Model):
        ...
        select_langs = models.ManyToManyField(ProgrammingLanguage)
        ...
        slug = models.UUIDField(default=uuid.uuid4)
    ...

forms.py

class ProjectForm(forms.Form):
...
select_lang = forms.ChoiceField(
    label='diller: ',
    widget=forms.CheckboxSelectMultiple()
)

def __init__(self, *args, **kwargs):
    super(ProjectForm, self).__init__(args, kwargs)



       self.fields['select_lang'].choices = [(l.id, l.name) for l in ProgrammingLanguage.objects.all()]


class Meta:
    model = Project
    fields = (
        'first_name', 'last_name', 'email', 'project_name', 'project_description', 'project_notes', 'select_langs')

And this is my traceback

Internal Server Error: /project/new/
Traceback (most recent call last):
  File "/home/eda/.local/lib/python2.7/site-packages/django/core/handlers/exception.py", line 41, in inner
    response = get_response(request)
  File "/home/eda/.local/lib/python2.7/site-packages/django/core/handlers/base.py", line 187, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/home/eda/.local/lib/python2.7/site-packages/django/core/handlers/base.py", line 185, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/eda/.local/lib/python2.7/site-packages/django/contrib/auth/decorators.py", line 23, in _wrapped_view
    return view_func(request, *args, **kwargs)
  File "/home/eda/staj_defteri/project/views.py", line 16, in project_new
    if form.is_valid():
  File "/home/eda/.local/lib/python2.7/site-packages/django/forms/forms.py", line 183, in is_valid
    return self.is_bound and not self.errors
  File "/home/eda/.local/lib/python2.7/site-packages/django/forms/forms.py", line 175, in errors
    self.full_clean()
  File "/home/eda/.local/lib/python2.7/site-packages/django/forms/forms.py", line 384, in full_clean
    self._clean_fields()
  File "/home/eda/.local/lib/python2.7/site-packages/django/forms/forms.py", line 396, in _clean_fields
    value = field.widget.value_from_datadict(self.data, self.files, self.add_prefix(name))
  File "/home/eda/.local/lib/python2.7/site-packages/django/forms/widgets.py", line 240, in value_from_datadict
    return data.get(name)
AttributeError: 'tuple' object has no attribute 'get'
[17/Sep/2018 08:19:35] "POST /project/new/ HTTP/1.1" 500 98194

Answer 1

The error is probably the fact that you call the super(ProjectForm, self).__init__ with args , and kwargs as two parameters, not with sequence unpacking and dictionary unpacking, like:

def __init__(self, *args, **kwargs):
    super(ProjectForm, self).__init__()
    self.fields['select_lang'].choices = [
        (l.id, l.name) for l in ProgrammingLanguage.objects.all()
    ]

In case you call it with args , etc. the first parameter will contain a (possibly empty) tuple as data parameter. If you then later aim to process the data , it will fail to do so.

That being said, I do not understand why you make it a forms.ChoiceField here. By default Django will pick a ModelMultipleChoiceField [Django-doc] field, and also take by default the entire collection of ProgrammingLanguage onbjects.