分配前引用的局部变量'context_dict'

Question

有人可以请我解释一下这个错误的含义吗？什么是任务？ context_dict应该在哪里？或者我犯了一些其他错误？我是Django的新手。非常感谢。

def add_page(request, category_name_slug): 
    try: 
     cat = Category.objects.get(slug=category_name_slug) 
    except Category.DoesNotExist: 
     cat = None 

    if request.method == 'POST': 
     form = PageForm(request.POST) 
     if form.is_valid(): 
      if cat: 
       page = form.save(commit=False) 
       page.category = cat 
       page.views = 0 
       page.save() 
       # probably better to use a redirect here. 
       return category(request, category_name_slug) 
      else: 
       print form.errors 
     else: 
      form = PageForm() 

     context_dict = {'form':form, 'category': cat} 

    return render(request, 'rango/add_page.html', context_dict) 

我得到这个错误：

local variable 'context_dict' referenced before assignment 

和异常指向我在符合收益渲染（reqyest， '兰戈/ add_page.html'，context_dict）

相同回溯

Answer 1

请记住，在Python中，缩进非常重要。问题是你的变量context_dict在if语句之外没有任何引用，因为它是如何缩进的。所以，你声明的变量context_dict为这样的if语句外：

context_dict = {} 
    if request.method == 'POST': 
    <rest of code here> 

Answer 2

试试此代码只回复POST请求。

def add_page(request, category_name_slug): 
    try: 
     cat = Category.objects.get(slug=category_name_slug) 
    except Category.DoesNotExist: 
     cat = None 

    if request.method == 'POST': 
     form = PageForm(request.POST) 
     if form.is_valid(): 
      if cat: 
       page = form.save(commit=False) 
       page.category = cat 
       page.views = 0 
       page.save() 
       # probably better to use a redirect here. 
       return category(request, category_name_slug) 
      else: 
       print form.errors 
     else: 
      form = PageForm() 

     context_dict = {'form':form, 'category': cat} 
     # indented - only reply to post requests 
     return render(request, 'rango/add_page.html', context_dict) 
    # if this is not a post request, raise an exception (handle your way later..) 
    raise Exception('NOT A POST REQUEST') 

Answer 3

我重新再分解我的代码和这样的作品。我的context_dict现在在if语句之外，而else：form = PageForm（）在外部if语句中，现在不像以前那样在内部if语句中。谢谢你们帮助我。

def add_page(request, category_name_slug): 
    try: 
     cat = Category.objects.get(slug=category_name_slug) 
    except Category.DoesNotExist: 
     cat = None 

    if request.method == 'POST': 
     form = PageForm(request.POST) 
     if form.is_valid(): 
      if cat: 
       page = form.save(commit=False) 
       page.category = cat 
       page.views = 0 
       page.save() 
       # probably better to use a redirect here. 
       return category(request, category_name_slug) 
      else: 
       print form.errors 
    else: 
     form = PageForm() 

    context_dict = {'category': cat, 'form': form} 

    return render(request, 'rango/add_page.html', context_dict)