尝试在视图中设置会话值时，为什么会出现 TypeError (Object ... is not JSON serializable)？
Why do I have a TypeError (Object ... is not JSON serializable) when trying to set a session value in a view?
当我尝试在视图中设置会话值时（在 basket应用程序）。 request.session['Hello'] = 'foo'.
出现错误
但是，这个错误不会出现在其他地方。例如，在store app中，在views.py中，下面的request.session['Hello World'] = 'Alloy'效果很好。
为什么会这样？
购物车应用 / views.py
from django.shortcuts import render, get_object_or_404
from django.http import JsonResponse
from . basket import Basket
from store.models import Product
from discount.forms import UserDiscountForm
def basket_summary(request):
basket = Basket(request)
context = {'basket':basket}
request.session['Hello'] = 'foo'
return render(request,"store/basket_summary.html",context)
def basket_add(request):
basket = Basket(request)
if request.POST.get('action') == 'post':
product_id = int(request.POST.get('productid'))
product_qty = int(request.POST.get('productqty'))
product = get_object_or_404(Product, id=product_id)
basket.add(product=product, qty=product_qty)
basketqty = basket.__len__()
response = JsonResponse({'qty':basketqty})
return response
def basket_add_new(request):
basket = Basket(request)
if request.POST.get('action') == 'post':
product_id = int(request.POST.get('productid'))
product = get_object_or_404(Product, id=product_id)
basket.add_new(product=product)
basketqty = basket.__len__()
response = JsonResponse({'qty':basketqty})
return response
def basket_delete(request):
basket = Basket(request)
if request.POST.get('action') == 'post':
product_id = int(request.POST.get('productid'))
basket.delete(product=product_id)
basketqty = basket.__len__()
baskettotal = basket.get_total_price()
response = JsonResponse({'qty':basketqty, 'subtotal':baskettotal})
return response
def basket_update(request):
basket = Basket(request)
if request.POST.get('action') == 'update-basket':
product_id = int(request.POST.get('productid'))
product_qty = int(request.POST.get('productqty'))
basket.update(product=product_id, qty=product_qty)
basketqty = basket.__len__()
baskettotal = basket.get_total_price()
itemtotal = basket.get_subtotal_price(product=product_id)
response = JsonResponse({'qty':basketqty, 'baskettotal':baskettotal, 'product_qty':product_qty, 'itemtotal':itemtotal})
return response
购物车应用 / basket.py
from decimal import Decimal
from store.models import Product
class Basket():
def __init__(self, request):
self.session = request.session
basket = self.session.get('cart')
if 'cart' not in request.session:
basket = self.session['cart'] = {}
self.basket = basket
def save(self):
self.session.modified = True
def add(self, product, qty):
"""
Adding and updating basket session data
"""
product_id = str(product.id)
price = float(product.price)
subtotal = qty * price
if product_id not in self.basket:
self.basket[product_id] = {'price': price, 'qty':int(qty), 'subtotal': subtotal}
else:
self.basket[product_id]['qty'] = qty
self.basket[product_id]['subtotal'] = subtotal
self.save()
def add_new(self, product):
"""
Adding new item in basket session data
"""
product_id = str(product.id)
if product_id not in self.basket:
self.basket[product_id] = {'price': float(product.price), 'qty':1, 'subtotal':float(product.price)}
# self.basket[product_id] = {'price': float(product.price), 'qty':1}
else:
pass
self.save()
def __iter__(self):
"""
Collect the product_id in the session data to query the database and return products
"""
product_ids = self.basket.keys()
products = Product.objects.filter(id__in=product_ids)
basket = self.basket.copy()
for product in products:
basket[str(product.id)]['product'] = product
for item in basket.values():
item['price'] = float(item['price'])
item['total_price'] = item['price'] * item['qty']
yield item
def __len__(self):
"""
Get the basket data and count the quantity of all items
"""
return sum(item['qty'] for item in self.basket.values())
def get_total_price(self):
return sum(float(item['price']) * item['qty'] for item in self.basket.values())
def get_subtotal_price(self, product):
product_id = str(product)
return self.basket[product_id]['qty'] * self.basket[product_id]['price']
def delete(self, product):
"""
Delete item from session data
"""
product_id = str(product)
if product_id in self.basket:
del self.basket[product_id]
self.save()
def update(self, product, qty):
"""
Update item in session data
"""
product_id = str(product)
if product_id in self.basket:
self.basket[product_id]['qty'] = qty
self.basket[product_id]['subtotal'] = self.basket[product_id]['qty'] * self.basket[product_id]['price']
self.save()
def clear(self):
try:
del self.session['cart']
except KeyError:
pass
self.save()
应用商店/models.py
from django.db import models
from django.urls import reverse
class Category(models.Model):
name = models.CharField(max_length=254, db_index=True)
slug = models.SlugField(max_length=254, unique = True)
class Meta:
verbose_name_plural = 'categories'
def __str__(self):
return self.name
class Product(models.Model):
category = models.ForeignKey(Category, related_name='product', on_delete=models.CASCADE)
title = models.CharField(max_length=254)
description = models.TextField(blank=True)
image = models.ImageField(upload_to='images/', default='images/default.png')
slug = models.SlugField(max_length=254, unique = True)
price = models.DecimalField(max_digits=5, decimal_places=2)
is_active = models.BooleanField(default=True)
created = models.DateTimeField(auto_now_add=True)
updated = models.DateTimeField(auto_now=True)
image2 = models.ImageField(upload_to='images/', null=True, blank=True)
image3 = models.ImageField(upload_to='images/', null=True, blank=True)
stock = models.IntegerField()
weight = models.IntegerField(verbose_name='Poids (g)')
class Meta:
verbose_name_plural = 'products'
ordering = ('-created', ) # ordering in descending order
def get_absolute_url(self):
return reverse('store:product_detail', args=[self.slug])
def __str__(self):
return self.title
应用商店/views.py
from django.shortcuts import get_object_or_404, render
from requests.sessions import session
from .models import Category, Product
def home(request):
print('----------// HOME PAGE //----------')
request.session['Hello World'] = 'Alloy'
context = {}
return render(request, 'store/home.html', context)
def categories(request):
categories = Category.objects.all()
context = {'categories': categories}
return render(request, 'store/categories.html', context)
def all_products(request):
products = Product.objects.all()
context = {'products': products}
return render(request, 'store/all_products.html', context)
def product_detail(request, slug):
product = get_object_or_404(Product, slug=slug, is_active=True)
context = {'product': product}
return render(request, 'store/product_details.html', context)
回溯
Environment:
Request Method: GET
Request URL: http://127.0.0.1:8000/basket/
Django Version: 3.2
Python Version: 3.9.4
Installed Applications:
['django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
'store',
'account',
'basket',
'orders',
'payment',
'contact',
'address',
'discount',
'shipping']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.middleware.common.CommonMiddleware',
'django.middleware.csrf.CsrfViewMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'django.contrib.messages.middleware.MessageMiddleware',
'django.middleware.clickjacking.XFrameOptionsMiddleware']
Traceback (most recent call last):
File "C:\Users\Utilisateur\Documents\Environments\monoi_django_virtualenv\lib\site-packages\django\core\handlers\exception.py", line 47, in inner
response = get_response(request)
File "C:\Users\Utilisateur\Documents\Environments\monoi_django_virtualenv\lib\site-packages\django\utils\deprecation.py", line 119, in __call__
response = self.process_response(request, response)
File "C:\Users\Utilisateur\Documents\Environments\monoi_django_virtualenv\lib\site-packages\django\contrib\sessions\middleware.py", line 61, in process_response
request.session.save()
File "C:\Users\Utilisateur\Documents\Environments\monoi_django_virtualenv\lib\site-packages\django\contrib\sessions\backends\db.py", line 83, in save
obj = self.create_model_instance(data)
File "C:\Users\Utilisateur\Documents\Environments\monoi_django_virtualenv\lib\site-packages\django\contrib\sessions\backends\db.py", line 70, in create_model_instance
session_data=self.encode(data),
File "C:\Users\Utilisateur\Documents\Environments\monoi_django_virtualenv\lib\site-packages\django\contrib\sessions\backends\base.py", line 114, in encode
return signing.dumps(
File "C:\Users\Utilisateur\Documents\Environments\monoi_django_virtualenv\lib\site-packages\django\core\signing.py", line 110, in dumps
return TimestampSigner(key, salt=salt).sign_object(obj, serializer=serializer, compress=compress)
File "C:\Users\Utilisateur\Documents\Environments\monoi_django_virtualenv\lib\site-packages\django\core\signing.py", line 172, in sign_object
data = serializer().dumps(obj)
File "C:\Users\Utilisateur\Documents\Environments\monoi_django_virtualenv\lib\site-packages\django\core\signing.py", line 87, in dumps
return json.dumps(obj, separators=(',', ':')).encode('latin-1')
File "c:\users\utilisateur\appdata\local\programs\python\python39\lib\json\__init__.py", line 234, in dumps
return cls(
File "c:\users\utilisateur\appdata\local\programs\python\python39\lib\json\encoder.py", line 199, in encode
chunks = self.iterencode(o, _one_shot=True)
File "c:\users\utilisateur\appdata\local\programs\python\python39\lib\json\encoder.py", line 257, in iterencode
return _iterencode(o, 0)
File "c:\users\utilisateur\appdata\local\programs\python\python39\lib\json\encoder.py", line 179, in default
raise TypeError(f'Object of type {o.__class__.__name__} '
Exception Type: TypeError at /basket/
Exception Value: Object of type Product is not JSON serializable
问题出在您的 Basket class 的 __iter__ 方法中。我相信您在模板中迭代了篮子对象，因此在请求中使用了它（因为视图中没有循环）。
现在这个方法有什么问题？好吧，你有这个特定的行 basket = self.basket.copy()，它的作用是，它对字典进行了 浅拷贝 ，即引用的内部对象是相同的，但是你有一个嵌套字典，这意味着当你改变嵌套字典时，你实际上改变了你购物篮中的同一个字典！您可以使用 copy.deepcopy [Python docs] 制作字典的 深拷贝 ：
import copy
def __iter__(self):
...
<b>basket = copy.deepcopy(self.basket)</b>
...
</pre>
当我尝试在视图中设置会话值时（在 basket应用程序）。 request.session['Hello'] = 'foo'.
但是，这个错误不会出现在其他地方。例如，在store app中，在views.py中，下面的request.session['Hello World'] = 'Alloy'效果很好。
为什么会这样？
购物车应用 / views.py
from django.shortcuts import render, get_object_or_404
from django.http import JsonResponse
from . basket import Basket
from store.models import Product
from discount.forms import UserDiscountForm
def basket_summary(request):
basket = Basket(request)
context = {'basket':basket}
request.session['Hello'] = 'foo'
return render(request,"store/basket_summary.html",context)
def basket_add(request):
basket = Basket(request)
if request.POST.get('action') == 'post':
product_id = int(request.POST.get('productid'))
product_qty = int(request.POST.get('productqty'))
product = get_object_or_404(Product, id=product_id)
basket.add(product=product, qty=product_qty)
basketqty = basket.__len__()
response = JsonResponse({'qty':basketqty})
return response
def basket_add_new(request):
basket = Basket(request)
if request.POST.get('action') == 'post':
product_id = int(request.POST.get('productid'))
product = get_object_or_404(Product, id=product_id)
basket.add_new(product=product)
basketqty = basket.__len__()
response = JsonResponse({'qty':basketqty})
return response
def basket_delete(request):
basket = Basket(request)
if request.POST.get('action') == 'post':
product_id = int(request.POST.get('productid'))
basket.delete(product=product_id)
basketqty = basket.__len__()
baskettotal = basket.get_total_price()
response = JsonResponse({'qty':basketqty, 'subtotal':baskettotal})
return response
def basket_update(request):
basket = Basket(request)
if request.POST.get('action') == 'update-basket':
product_id = int(request.POST.get('productid'))
product_qty = int(request.POST.get('productqty'))
basket.update(product=product_id, qty=product_qty)
basketqty = basket.__len__()
baskettotal = basket.get_total_price()
itemtotal = basket.get_subtotal_price(product=product_id)
response = JsonResponse({'qty':basketqty, 'baskettotal':baskettotal, 'product_qty':product_qty, 'itemtotal':itemtotal})
return response
购物车应用 / basket.py
from decimal import Decimal
from store.models import Product
class Basket():
def __init__(self, request):
self.session = request.session
basket = self.session.get('cart')
if 'cart' not in request.session:
basket = self.session['cart'] = {}
self.basket = basket
def save(self):
self.session.modified = True
def add(self, product, qty):
"""
Adding and updating basket session data
"""
product_id = str(product.id)
price = float(product.price)
subtotal = qty * price
if product_id not in self.basket:
self.basket[product_id] = {'price': price, 'qty':int(qty), 'subtotal': subtotal}
else:
self.basket[product_id]['qty'] = qty
self.basket[product_id]['subtotal'] = subtotal
self.save()
def add_new(self, product):
"""
Adding new item in basket session data
"""
product_id = str(product.id)
if product_id not in self.basket:
self.basket[product_id] = {'price': float(product.price), 'qty':1, 'subtotal':float(product.price)}
# self.basket[product_id] = {'price': float(product.price), 'qty':1}
else:
pass
self.save()
def __iter__(self):
"""
Collect the product_id in the session data to query the database and return products
"""
product_ids = self.basket.keys()
products = Product.objects.filter(id__in=product_ids)
basket = self.basket.copy()
for product in products:
basket[str(product.id)]['product'] = product
for item in basket.values():
item['price'] = float(item['price'])
item['total_price'] = item['price'] * item['qty']
yield item
def __len__(self):
"""
Get the basket data and count the quantity of all items
"""
return sum(item['qty'] for item in self.basket.values())
def get_total_price(self):
return sum(float(item['price']) * item['qty'] for item in self.basket.values())
def get_subtotal_price(self, product):
product_id = str(product)
return self.basket[product_id]['qty'] * self.basket[product_id]['price']
def delete(self, product):
"""
Delete item from session data
"""
product_id = str(product)
if product_id in self.basket:
del self.basket[product_id]
self.save()
def update(self, product, qty):
"""
Update item in session data
"""
product_id = str(product)
if product_id in self.basket:
self.basket[product_id]['qty'] = qty
self.basket[product_id]['subtotal'] = self.basket[product_id]['qty'] * self.basket[product_id]['price']
self.save()
def clear(self):
try:
del self.session['cart']
except KeyError:
pass
self.save()
应用商店/models.py
from django.db import models
from django.urls import reverse
class Category(models.Model):
name = models.CharField(max_length=254, db_index=True)
slug = models.SlugField(max_length=254, unique = True)
class Meta:
verbose_name_plural = 'categories'
def __str__(self):
return self.name
class Product(models.Model):
category = models.ForeignKey(Category, related_name='product', on_delete=models.CASCADE)
title = models.CharField(max_length=254)
description = models.TextField(blank=True)
image = models.ImageField(upload_to='images/', default='images/default.png')
slug = models.SlugField(max_length=254, unique = True)
price = models.DecimalField(max_digits=5, decimal_places=2)
is_active = models.BooleanField(default=True)
created = models.DateTimeField(auto_now_add=True)
updated = models.DateTimeField(auto_now=True)
image2 = models.ImageField(upload_to='images/', null=True, blank=True)
image3 = models.ImageField(upload_to='images/', null=True, blank=True)
stock = models.IntegerField()
weight = models.IntegerField(verbose_name='Poids (g)')
class Meta:
verbose_name_plural = 'products'
ordering = ('-created', ) # ordering in descending order
def get_absolute_url(self):
return reverse('store:product_detail', args=[self.slug])
def __str__(self):
return self.title
应用商店/views.py
from django.shortcuts import get_object_or_404, render
from requests.sessions import session
from .models import Category, Product
def home(request):
print('----------// HOME PAGE //----------')
request.session['Hello World'] = 'Alloy'
context = {}
return render(request, 'store/home.html', context)
def categories(request):
categories = Category.objects.all()
context = {'categories': categories}
return render(request, 'store/categories.html', context)
def all_products(request):
products = Product.objects.all()
context = {'products': products}
return render(request, 'store/all_products.html', context)
def product_detail(request, slug):
product = get_object_or_404(Product, slug=slug, is_active=True)
context = {'product': product}
return render(request, 'store/product_details.html', context)
回溯
Environment:
Request Method: GET
Request URL: http://127.0.0.1:8000/basket/
Django Version: 3.2
Python Version: 3.9.4
Installed Applications:
['django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
'store',
'account',
'basket',
'orders',
'payment',
'contact',
'address',
'discount',
'shipping']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.middleware.common.CommonMiddleware',
'django.middleware.csrf.CsrfViewMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'django.contrib.messages.middleware.MessageMiddleware',
'django.middleware.clickjacking.XFrameOptionsMiddleware']
Traceback (most recent call last):
File "C:\Users\Utilisateur\Documents\Environments\monoi_django_virtualenv\lib\site-packages\django\core\handlers\exception.py", line 47, in inner
response = get_response(request)
File "C:\Users\Utilisateur\Documents\Environments\monoi_django_virtualenv\lib\site-packages\django\utils\deprecation.py", line 119, in __call__
response = self.process_response(request, response)
File "C:\Users\Utilisateur\Documents\Environments\monoi_django_virtualenv\lib\site-packages\django\contrib\sessions\middleware.py", line 61, in process_response
request.session.save()
File "C:\Users\Utilisateur\Documents\Environments\monoi_django_virtualenv\lib\site-packages\django\contrib\sessions\backends\db.py", line 83, in save
obj = self.create_model_instance(data)
File "C:\Users\Utilisateur\Documents\Environments\monoi_django_virtualenv\lib\site-packages\django\contrib\sessions\backends\db.py", line 70, in create_model_instance
session_data=self.encode(data),
File "C:\Users\Utilisateur\Documents\Environments\monoi_django_virtualenv\lib\site-packages\django\contrib\sessions\backends\base.py", line 114, in encode
return signing.dumps(
File "C:\Users\Utilisateur\Documents\Environments\monoi_django_virtualenv\lib\site-packages\django\core\signing.py", line 110, in dumps
return TimestampSigner(key, salt=salt).sign_object(obj, serializer=serializer, compress=compress)
File "C:\Users\Utilisateur\Documents\Environments\monoi_django_virtualenv\lib\site-packages\django\core\signing.py", line 172, in sign_object
data = serializer().dumps(obj)
File "C:\Users\Utilisateur\Documents\Environments\monoi_django_virtualenv\lib\site-packages\django\core\signing.py", line 87, in dumps
return json.dumps(obj, separators=(',', ':')).encode('latin-1')
File "c:\users\utilisateur\appdata\local\programs\python\python39\lib\json\__init__.py", line 234, in dumps
return cls(
File "c:\users\utilisateur\appdata\local\programs\python\python39\lib\json\encoder.py", line 199, in encode
chunks = self.iterencode(o, _one_shot=True)
File "c:\users\utilisateur\appdata\local\programs\python\python39\lib\json\encoder.py", line 257, in iterencode
return _iterencode(o, 0)
File "c:\users\utilisateur\appdata\local\programs\python\python39\lib\json\encoder.py", line 179, in default
raise TypeError(f'Object of type {o.__class__.__name__} '
Exception Type: TypeError at /basket/
Exception Value: Object of type Product is not JSON serializable
问题出在您的 Basket class 的 __iter__ 方法中。我相信您在模板中迭代了篮子对象，因此在请求中使用了它（因为视图中没有循环）。
现在这个方法有什么问题？好吧，你有这个特定的行 basket = self.basket.copy()，它的作用是，它对字典进行了 浅拷贝 ，即引用的内部对象是相同的，但是你有一个嵌套字典，这意味着当你改变嵌套字典时，你实际上改变了你购物篮中的同一个字典！您可以使用 copy.deepcopy [Python docs] 制作字典的 深拷贝 ：
import copy
def __iter__(self):
...
<b>basket = copy.deepcopy(self.basket)</b>
...
</pre>