Python/Django makemigrations E版

Question

我最近一直在研究Python和Django，下面是本教程-https://www.codementor.io/jadianes/get-started-with-django-building-recommendation-review-app-du107yb1a

我会改变这个应用程序，只是为了试验，但是我在“makemigrations”上有点停滞不前。在

当我运行python manage.py makemigrations reviews时，我得到如下回溯：

 Traceback (most recent call last):   File "manage.py", line 15, in
 <module>
     execute_from_command_line(sys.argv)   File "C:\Users\CalPC\AppData\Local\Programs\Python\Python36\lib\site-packages\django\core\management\__init__.py",
 line 371, in execute_from_command_line
     utility.execute()   File "C:\Users\CalPC\AppData\Local\Programs\Python\Python36\lib\site-packages\django\core\management\__init__.py",
 line 347, in execute
     django.setup()   File "C:\Users\CalPC\AppData\Local\Programs\Python\Python36\lib\site-packages\django\__init__.py",
 line 24, in setup
     apps.populate(settings.INSTALLED_APPS)   File "C:\Users\CalPC\AppData\Local\Programs\Python\Python36\lib\site-packages\django\apps\registry.py",
 line 112, in populate
     app_config.import_models()   File "C:\Users\CalPC\AppData\Local\Programs\Python\Python36\lib\site-packages\django\apps\config.py",
 line 198, in import_models
     self.models_module = import_module(models_module_name)   File "C:\Users\CalPC\AppData\Local\Programs\Python\Python36\lib\importlib\__init__.py",
 line 126, in import_module
     return _bootstrap._gcd_import(name[level:], package, level)   File "<frozen importlib._bootstrap>", line 994, in _gcd_import   File
 "<frozen importlib._bootstrap>", line 971, in _find_and_load   File
 "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked 
 File "<frozen importlib._bootstrap>", line 665, in _load_unlocked  
 File "<frozen importlib._bootstrap_external>", line 678, in
 exec_module   File "<frozen importlib._bootstrap>", line 219, in
 _call_with_frames_removed   File "C:\Users\CalPC\Desktop\review_app\prodreview\reviews\models.py", line
 2, in <module>
     import numpy as np ModuleNotFoundError: No module named 'numpy'

这是我的模型

^{pr2}$

我运行的是Django 2.0和python3.6.5

如果有人能指出我可能出错的地方，那就太好了。在

提前谢谢！在

Answer 1

如果只使用numpy来计算平均值，则不需要numpy。您可以改为使用^{}。在

import statistics

class Product(models.Model):
    name = models.CharField(max_length=200)

    def average_rating(self):
        all_ratings = map(lambda x: x.rating, self.review_set.all())
        return statistics.mean(all_ratings)

您还可以使用^{}让数据库计算平均值。在

^{pr2}$

或者，^{}可以很有用，如果你想得到查询集中每个产品的平均值。在

Product.objects.annotate(avg_rating=Avg('review__rating'))

Answer 2

确保numpy在您的需求文件中，然后pip install -r requirements.txt