Python 当试图设置django会话值时，我遇到了类型错误"；Decimal类型的对象不可JSON序列化；而它是一个字符串值。为什么？

我想记录输入用户的折扣代码。我已经设置了一个UserDiscountForm（forms.Form）（在forms.py中）。在视图中，我希望在会话中记录用户输入的数据。但当我尝试设置值时（在检查表单是否有效之后），它会引发一个TypeError：“Decimal类型的对象不可JSON序列化”。我不明白，因为我试图保存的数据是字符串值。此外，我还能够以类似的方式在会话中保存其他数据（购物车和发货地址），而且效果非常好

forms.py （用户输入是一个字符串）

views.py （form.cleaned_data['user_discount']是一个字符串）

回溯 我有一个ShippingAddressForm（forms.ModelForm），它工作得很好。以下是与其关联的视图

views.py 类Basket in Basket.py

---

请将完整的错误回溯添加到您的问题中。我已添加了回溯。您确定您使用的表单是正确的

UserDiscountForm

，或者您有另一个表单的名称与您错误使用的名称相同？我已仔细检查。我只有一个表单叫做UserDiscountForm。我想具体说明一下forms.py在一个名为“折扣”的应用程序中-views.py在一个名为“basket”的应用程序中我不认为这是个问题…你能分享

basket

类吗？

from django import forms

class UserDiscountForm(forms.Form):
    user_discount = forms.CharField(label='discount code ?', label_suffix="-->", help_text="Entrez discount code", required=False)

    def clean_user_discount(self, *args, **kwargs):
        user_input = self.cleaned_data['user_discount']

        if len(user_input) > 4:
            raise forms.ValidationError("longueur > 4")
        
        else:
            print(type(user_input))
            return user_input

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)
    form = UserDiscountForm(request.POST or None)
    context = {'basket':basket, 'form':form}
    if request.method == 'POST':
        if form.is_valid():
            print(form.cleaned_data['user_discount'])
            print(type(form.cleaned_data['user_discount']))
            request.session['discount_code'] = form.cleaned_data['user_discount']
            form = UserDiscountForm()
            context = {'basket':basket, 'form':form}
            return render(request,"store/basket_summary.html",context)
        else:
            return render(request,"store/basket_summary.html",context)
    else:
        return render(request,"store/basket_summary.html",context)

Environment:


Request Method: POST
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 Decimal is not JSON serializable

def check_existing_shipping_address(request):
    try:
        shipping_address_form_id = request.session['shipping-form-id']
        return redirect('address:update_shipping_address')
    except:
        return redirect('address:create_shipping_address')


def create_shipping_address(request):
    form = ShippingAddressForm(request.POST or None)
    context = {'form':form}

    if request.method == 'POST':
        if form.is_valid():
            shipping_form = form.save()
            request.session['shipping-form-id'] = shipping_form.pk
            shipping_form = ShippingAddressForm()            
            return redirect('payment:checkout')
        else:
            return render(request,"payment/shipping_address.html",context)
    else:
        return render(request,"payment/shipping_address.html",context)

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)

        if product_id not in self.basket:
            self.basket[product_id] = {'price': float(product.price), 'qty':int(qty)}

        else:
            self.basket[product_id]['qty'] = qty

        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}

        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'] = Decimal(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(Decimal(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.save()


    def clear(self):
        
        try:
            del self.session['cart']
        except KeyError:
            pass

        self.save()