Django (django_tables2) ValueError: Expected table or queryset, not str + for loop issue答案

【问题标题】：Django (django_tables2) ValueError: Expected table or queryset, not str + for loop issueDjango (django_tables2) ValueError: Expected table or queryset, not str + for loop issue
【发布时间】：2019-03-23 07:17:34
【问题描述】：

我有一个 Django 项目，它深受 Mozilla 的 Django 教程 (https://developer.mozilla.org/en-US/docs/Learn/Server-side/Django/Tutorial_local_library_website) 的影响。我已将books 修改为samples，每个samples 都隶属于研究员/pi（又名author）。我创建了一个名为Variant 的单独模型，它是Sample 模型的外键。由于此字段将允许每个样本有多个变体，因此在查看样本的详细视图时，我想将变体（特定于单个样本）显示为渲染表。我没有成功实现这一点，我认为我只是没有完全正确地获得视图命名法（以及 html 文件中的语言）。我的问题在这篇文章的最后。

这是我的代码。

samples/models.py

class Variant(models.Model):
   gene = models.CharField('Gene', max_length=100, blank=True, default='')
   variant = models.CharField('Variant', max_length=50, blank=True, default='')
   call = models.CharField('Call', max_length=100, blank=True, default='')
   position = models.IntegerField('Position', blank=True, null=True) 

   def __str__(self):
      return f'{self.gene}, {self.position}, {self.variant}, {self.call}'

class Sample(models.Model):
   sample_name = models.CharField('Sample', max_length=16)
   pi = models.ForeignKey(PI, on_delete=models.SET_NULL, null=True)
   sample_variant = models.ForeignKey(Variant, on_delete=models.SET_NULL, null=True) 
     .
     .
     .
   def __str__(self):
      return self.sample_name

   def get_absolute_url(self):
      return reverse('sample-detail', args=[str(self.id)])

tables.py

class SampleTable(tables.Table):
   sample_name = tables.LinkColumn('sample-detail', args=[A('pk')])
   pi = tables.LinkColumn('sample-detail', args=[A('pk')])

   class Meta:
      model = Sample
#----------------------------------------------------------------------------

#----------------------------------------------------------------------------
class PISampleTable(tables.Table):
   sample_name = tables.LinkColumn('sample-detail', args=[A('pk')])

   class Meta:
      model = Sample
#----------------------------------------------------------------------------

...
#----------------------------------------------------------------------------
class VariantTable(tables.Table):
   gene = tables.LinkColumn('sample-detail', args=[A('pk')])

   class Meta:
      model = Variant
#----------------------------------------------------------------------------

我不确定是否像我所做的那样设置基因（变异字段）是 copicide。

samples/views.py

class SampleListView(generic.ListView):
   model = Sample
   paginate_by = 100

@login_required
def sam(request):
   table = SampleTable(Sample.objects.all())
   RequestConfig(request).configure(table)
   return render(request, 'samples/sample_list.html', {'sam': table}) 
#-------------------------------------------------------------------------------------------------

#-------------------------------------------------------------------------------------------------
class SampleDetailView(generic.DetailView):
    model = Sample
#-------------------------------------------------------------------------------------------------

    ...
#-------------------------------------------------------------------------------------------------
class VariantListView(generic.ListView):
   model = Variant
   paginate_by = 100

@login_required
def var(request):
   #table = VariantTable(Variant.objects.filter(pi=pk))
   table = VariantTable(Variant.objects.all())
   RequestConfig(request).configure(table)
   return render(request, 'samples/sample_detail.html', {'var': table}) 
#-------------------------------------------------------------------------------------------------

samples/urls.py

urlpatterns = [ 
   path('', views.index, name='index'),
   path('samples/', views.sam, name='sam'),
   path('sample/<int:pk>', views.SampleDetailView.as_view(), name='sample-detail'),
   path('pi/', views.pi_table, name='pi_table'),
   path('pi/<int:pk>', views.pi_view, name='pi-detail'),
   path('samples/new', views.pi_new, name='pi_new'),
   path('samples/new_sample', views.sample_new, name='sample_new'),
   #path('samples/', views.var, name='var'),
   #path('samples/<int:pk>', views.var, name='var'),
   path('samples/', views.VariantListView.as_view(), name='var'),
]

samples/templates/samples/sample_detail.html

 {% extends "base_generic.html" %}
{% load render_table from django_tables2 %}

{% block content %}
   <h1>Sample: {{ sample.sample_name }}</h1>

   <p><strong>PI:</strong> <a href="{% url 'pi-detail' sample.pi.pk %}">{{ sample.pi }}</a></p>
   ...
   <h3>Variant Results</h3>
   <p><strong>(gene, position, variant, call):</strong> {{ sample.sample_variant }}</p> <!-- this works, but only last item in list-->


  <p><strong>Variant:</strong> {% for variant in sample.sample_variant.all %} {{ variant }}{% if not forloop.last %}, {% endif %}{% endfor %}</p>

  {% if sample.sample_variant %}
  <ul>

   {% for variant in variant_list %}
     <li> <a href="{{ variant.get_absolute_url }}">{{ variant.gene }}</a> ({{variant.call}})</li>
   {% endfor %}
  </ul>
  {% else %}
    <p>There are no variants for this sample.</p>                                                                                                                                    

  {% endif %}       

{% render_table var %}

{% endblock %}

为了测试它，我有一个样本，我添加了两个变体 - 但是，仅显示最后一个变体（可以理解）：

<p><strong>(gene, position, variant, call):</strong> {{ sample.sample_variant }}

循环代码是我正在玩的东西，但它根本不起作用，如果我将{% render_table var %} 行保留在那里，我会收到此错误：

  File "/opt/miniconda3/envs/py37/lib/python3.7/site-packages/django/template/response.py", line 83, in rendered_content
    content = template.render(context, self._request)
  File "/opt/miniconda3/envs/py37/lib/python3.7/site-packages/django/template/backends/django.py", line 61, in render
    return self.template.render(context)
  File "/opt/miniconda3/envs/py37/lib/python3.7/site-packages/django/template/base.py", line 171, in render
    return self._render(context)
  File "/opt/miniconda3/envs/py37/lib/python3.7/site-packages/django/template/base.py", line 163, in _render
    return self.nodelist.render(context)
  File "/opt/miniconda3/envs/py37/lib/python3.7/site-packages/django/template/base.py", line 937, in render
    bit = node.render_annotated(context)
  File "/opt/miniconda3/envs/py37/lib/python3.7/site-packages/django/template/base.py", line 904, in render_annotated
    return self.render(context)
  File "/opt/miniconda3/envs/py37/lib/python3.7/site-packages/django/template/loader_tags.py", line 150, in render
    return compiled_parent._render(context)
  File "/opt/miniconda3/envs/py37/lib/python3.7/site-packages/django/template/base.py", line 163, in _render
    return self.nodelist.render(context)
  File "/opt/miniconda3/envs/py37/lib/python3.7/site-packages/django/template/base.py", line 937, in render
    bit = node.render_annotated(context)
  File "/opt/miniconda3/envs/py37/lib/python3.7/site-packages/django/template/base.py", line 904, in render_annotated
    return self.render(context)
  File "/opt/miniconda3/envs/py37/lib/python3.7/site-packages/django/template/loader_tags.py", line 62, in render
    result = block.nodelist.render(context)
  File "/opt/miniconda3/envs/py37/lib/python3.7/site-packages/django/template/base.py", line 937, in render
    bit = node.render_annotated(context)
  File "/opt/miniconda3/envs/py37/lib/python3.7/site-packages/django/template/base.py", line 904, in render_annotated
    return self.render(context)
  File "/opt/miniconda3/envs/py37/lib/python3.7/site-packages/django_tables2/templatetags/django_tables2.py", line 148, in render
    raise ValueError("Expected table or queryset, not {}".format(klass))
ValueError: Expected table or queryset, not str

我了解我传递字符串而不是查询集/表类对象导致的错误，但我还没有想出如何解决它。

django_tables2 版本是最新的，并且可以毫无问题地呈现其他表。

我将gene 链接到列的方式与我在其他模型中的字段（sample_name 和pi）中所做的方式相似——是否正确？
如何安排 for 循环以正确显示列表中的所有变体？
我需要在（假设）views.py 文件中进行哪些更改才能正确呈现var 表？
我不相信我在 urls.py 中正确列出了路径（我尝试了几种变体但没有成功），如果不正确，应该如何正确构建它？

非常感谢和感谢任何帮助。

【问题讨论】：

请发布完整的回溯。
@WillemVanOnsem 如果我使用这种方法：stackoverflow.com/questions/4839762/…，我应该将它添加到哪个文件？

标签： django django-models django-views django-tables2

【解决方案1】：

好的 -- 非常感谢帮助我找到错误的朋友 (AR)。

第一个问题是我的关系不正确；外键需要在Variant 模型中，而不是Sample 模型中（Sample 模型中的sample_variant 已删除）。

models.py

class Variant(models.Model):                                                              
   gene = models.CharField('Gene', max_length=100, blank=True, default='')
   nucleotide_variant = models.CharField('Variant', max_length=50, blank=True, default='')   call = models.CharField('Call', max_length=100, blank=True, default='')
   position = models.IntegerField('Position', blank=True, null=True) 
   sample_n = models.ForeignKey(Sample, on_delete=models.SET_NULL, null=True)

   class Meta:
      ordering = ('sample_n', 'gene', 'position', 'nucleotide_variant', 'call')

   def __str__(self):
      return f'{self.sample_n}, {self.gene}, {self.position}, {self.nucleotide_variant}, {self.call}'

接下来我将字段variant 更改为nucleotide_variant。这可能是不必要的，但它让我更清楚。

views.py

class VariantListView(generic.ListView):
   model = Variant
   paginate_by = 100 

@login_required
def var(request):
   variant = Variant.objects.get(pk = pk) 
   table = VariantTable(Variant.objects.filter(variant=pk))
   RequestConfig(request).configure(table)                                                
   return render(request, 'samples/sample_detail.html', {'variant': variant, 'var': table})

urls.py

path('samples/', views.var, name='var'),

html

   <h3>Variant Results</h3>
   {% render_table sample.variant_set.all %}

问题已解决，表格已呈现。

【讨论】：