问反转视图失败，因为参数为None。

EN

class CarownerTable(tables.Table):
    ...
    Car_registration=tables.LinkColumn('register_docs', args =[A('register__id')], text='View Register', orderable=False)

url(r'^register_docs/$', views.register_docs, name='register_docs' ),
url(r'^register_docs/(?P<docid>(\d)+)$', views.register_docs, name='register_docs' ),

def register_docs(request, docid=None):
    #This view allows for the display of the pdf file
    if docid is None:
        #this line here loads a default image
        doclink = '........./Car/Misc/noImageOnFile.pdf'
        return HttpResponse(doclink, content_type="application/pdf")
    else:
        register_doc_path = Register.objects.get(pk=docid).register_File_Path

        register_doc_data = open(register_doc_path, "rb").read()
        t = loader.get_template('carmanager/display_docs.html')
        variables = RequestContext(request, {'file':register_doc_data})
        output = t.render(variables)
        return HttpResponse(register_doc_data, content_type="application/pdf")

Reverse for 'register_docs' with arguments '(None,)' and keyword arguments '{}' not found. 2 pattern(s) tried: ['carmanager/register_docs/(?P<docid>(\\d)+)$', 'carmanager/register_docs$']