Djangoのクエリーセットにすべての値を追加します

Question

私は、レビューとそのレビューへの返信の2つのクラスを持つdjangoアプリを作成しています。返信はレビューのManyToManyフィールドに格納されます。

これは、レビューのために、私のクラスである：

class Review(models.Model): 
    title = models.CharField(max_length = 30) 
    replies = models.ManyToManyField(Reply) 

    def __str__(self): 
     return self.title 

そして、ここでは私の返事クラスです：私がやりたいことの

class Reply(models.Model): 
    rating = models.DecimalField(decimal_places=1, 
           max_digits = 2, 
           validators = [MaxValueValidator(5), MinValueValidator(0)], 
           default = 0 
           ) 
    text_reply = models.TextField(max_length = 200) 

一つ、Aのすべての評価を取ることですこれらの数値の平均を計算します。

result = {} 
objects = Review.objects.all() 
for review in objects: 
    average = 0 
    length = 0 
    for reply in review​.replies.all(): 
     average += reply.rating 
     length += 1 
    average /= length 
    result.update({review.title, average}) 

は、モデルの属性を探している場合は、特定のレビューのための評価を計算するための

def calculate_average(): 
    objects = Review.objects.all() 
    average = 0 
    length = 0 
    for reply in objects: 
     average += reply.replies.rating 
     length += 1 
    return average/length 

トレースバック

C:\Users\Will Treston\gd\LesRev\lesssonreview>python manage.py runserver 
Unhandled exception in thread started by <function check_errors.<locals>.wrapper at 0x03363540> 
Traceback (most recent call last): 
    File "C:\Users\Will Treston\AppData\Local\Programs\Python\Python36-32\lib\site-packages\django\utils\autoreload.py", line 226, in wrapper 
    fn(*args, **kwargs) 
    File "C:\Users\Will Treston\AppData\Local\Programs\Python\Python36-32\lib\site-packages\django\core\management\commands\runserver.py", line 113, in inner_run 
    autoreload.raise_last_exception() 
    File "C:\Users\Will Treston\AppData\Local\Programs\Python\Python36-32\lib\site-packages\django\utils\autoreload.py", line 249, in raise_last_exception 
    six.reraise(*_exception) 
    File "C:\Users\Will Treston\AppData\Local\Programs\Python\Python36-32\lib\site-packages\django\utils\six.py", line 685, in reraise 
    raise value.with_traceback(tb) 
    File "C:\Users\Will Treston\AppData\Local\Programs\Python\Python36-32\lib\site-packages\django\utils\autoreload.py", line 226, in wrapper 
    fn(*args, **kwargs) 
    File "C:\Users\Will Treston\AppData\Local\Programs\Python\Python36-32\lib\site-packages\django\__init__.py", line 27, in setup 
    apps.populate(settings.INSTALLED_APPS) 
    File "C:\Users\Will Treston\AppData\Local\Programs\Python\Python36-32\lib\site-packages\django\apps\registry.py", line 115, in populate 
    app_config.ready() 
    File "C:\Users\Will Treston\AppData\Local\Programs\Python\Python36-32\lib\site-packages\django\contrib\admin\apps.py", line 23, in ready 
    self.module.autodiscover() 
    File "C:\Users\Will Treston\AppData\Local\Programs\Python\Python36-32\lib\site-packages\django\contrib\admin\__init__.py", line 26, in autodiscover 
    autodiscover_modules('admin', register_to=site) 
    File "C:\Users\Will Treston\AppData\Local\Programs\Python\Python36-32\lib\site-packages\django\utils\module_loading.py", line 50, in autodiscover_modules 
    import_module('%s.%s' % (app_config.name, module_to_search)) 
    File "C:\Users\Will Treston\AppData\Local\Programs\Python\Python36-32\lib\importlib\__init__.py", line 126, in import_module 
    return _bootstrap._gcd_import(name[level:], package, level) 
    File "<frozen importlib._bootstrap>", line 978, in _gcd_import 
    File "<frozen importlib._bootstrap>", line 961, in _find_and_load 
    File "<frozen importlib._bootstrap>", line 950, in _find_and_load_unlocked 
    File "<frozen importlib._bootstrap>", line 655, in _load_unlocked 
    File "<frozen importlib._bootstrap_external>", line 678, in exec_module 
    File "<frozen importlib._bootstrap>", line 205, in _call_with_frames_removed 
    File "C:\Users\Will Treston\gd\LesRev\lesssonreview\review\admin.py", line 5, in <module> 
    class ReviewAdmin(admin.ModelAdmin): 
    File "C:\Users\Will Treston\gd\LesRev\lesssonreview\review\admin.py", line 8, in ReviewAdmin 
    list_display = ["title", Review.calculate_average()] 
    File "C:\Users\Will Treston\gd\LesRev\lesssonreview\review\models.py", line 46, in calculate_average 
    average += reply.replies.rating 
AttributeError: 'ManyRelatedManager' object has no attribute 'rating' 

Answer 1

：私はこれを行うことによってこれを行うことを試みました単一のモデルを同じに計算するには、

class Review(models.Model): 

    def calculate_rating(self): 
     average = 0 
     length = 0 
     for reply in self​.replies.all(): 
      average += reply.rating 
      length += 1 
     if average: 
      average /= length 
     return average