我如何解决ValueError：太多的值无法在Django中解包（预期2）

问题描述 投票：0回答：1

我一直在Django应用程序中工作。基本上，该应用程序的功能是使用表单从用户那里获取输入作为主题名称，获取该特定用户该主题的进度活动的详细信息，并将每个详细信息保存在单个变量中。它涉及3个模型，即。用户模型（Django的默认值）主题模型和详细信息模型，最后它将使用分配了详细信息的那些变量，并使用fuzz_algo()计算性能，然后以消息的形式将结果返回到模板。

一切似乎都很好，但是当我单击模板users/performance_calculator.html中的计算按钮时，它在ValueError: too many values to unpack (expected 2)中的此语句skype = Detail.objects.filter(subject__subject=sub, user__username=User.username).get('skype_session_attendance')处给出此错误views.py

我的views.py：

from django.shortcuts import render, redirect
from django.contrib import messages
from .forms import UserRegisterForm, UserUpdateForm, ProfileUpdateForm, PerformanceCalculatorForm
from django.contrib.auth.decorators import login_required
from django.contrib.auth.models import User
from .models import Subject, Detail
from .fuzzy_logic_algo import fuzz_algo

def register(request):
    if request.method == 'POST':
        form = UserRegisterForm(request.POST)
        if form.is_valid():
            form.save()
            username = form.cleaned_data.get('username')
            messages.success(request, f'Your Student Account has been created! You can log in ESACP now.')
            return redirect('login')
    else:
        form = UserRegisterForm()
    return render(request, 'users/register.html', {'form': form})

@login_required
def profile(request):
    if request.method == 'POST':
        u_form = UserUpdateForm(request.POST, instance=request.user)
        p_form = ProfileUpdateForm(request.POST,
            request.FILES,
            instance=request.user.profile)

        if u_form.is_valid() and p_form.is_valid():
            u_form.save()
            p_form.save()
            messages.success(request, f'Your Profile information has been updated.')
            return redirect('profile')

    else:
        u_form = UserUpdateForm(instance=request.user)
        p_form = ProfileUpdateForm(instance=request.user.profile)

    context = {
        'u_form': u_form,
        'p_form': p_form
    }

    return render(request, 'users/profile.html', context)


def performanceCalculator(request):
    skype = 0
    internal_course = 0
    prg_lab = 0
    mid_marks = 0
    final_marks = 0
    sub = 0
    if request.method == 'POST':
        performance_form = PerformanceCalculatorForm(request.POST)

        if performance_form.is_valid():
            performance_form.save()

            sub = performance_form.cleaned_data.get('subject')
            skype = Detail.objects.filter(subject__subject=sub, user__username=User.username).get('skype_session_attendance')
            internal_course = Detail.objects.filter(subject__subject=sub, user__username=User.username).get('internal_course_marks')
            prg_lab = Detail.objects.filter(subject__subject=sub, user__username=User.username).get('programming_lab_activity')
            mid_marks = Detail.objects.filter(subject__subject=sub, user__username=User.username).get('mid_term_marks')
            final_marks = Detail.objects.filter(subject__subject=sub, user__username=User.username).get('final_term_marks')

            result = fuzz_algo(skype, internal_course, prg_lab, mid_marks, final_marks)

            messages.success(request, result)

            return redirect('performance_calculator')
    else:
        performance_form = PerformanceCalculatorForm()

    context = {
        'performance_form': performance_form
    }

    return render(request, 'users/performance_calculator.html', context)

我的模型。py：

from django.db import models
from django.contrib.auth.models import User

class Subject(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    subject = models.CharField(max_length=100)

    def __str__(self):
        return '{} ({})'.format(self.subject, self.user.username)


class Detail(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    subject = models.OneToOneField(Subject, on_delete=models.CASCADE)
    skype_session_attendance = models.FloatField()
    internal_course_marks = models.FloatField()
    programming_lab_activity = models.FloatField()
    mid_term_marks = models.FloatField()
    final_term_marks = models.FloatField()

    def __str__(self):
        return f'{self.subject, (self.user.username)} Details'

class Sub(models.Model):
    s = models.CharField(max_length=100)

我的forms.py：

from django import forms
from .models import Profile, Sub

class PerformanceCalculatorForm(forms.ModelForm):
    subject = forms.CharField(max_length=100)

    class Meta:
        model = Sub
        fields = ['subject']

我的performance_calculator.html（模板）：

{% load static %}
{% load crispy_forms_tags %}
<!DOCTYPE html>
<html>
    <head>
        <!-- Required meta tags -->
        <meta charset="utf-8">
        <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

        <!-- Bootstrap CSS -->
        <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
        <link rel="stylesheet" type="text/css" href="{% static 'esacp/main.css' %}">

        <title>Expert System for Assessing Programming Course Performance</title>
    </head>

    <body>        
        <main role="main" class="container">
            <div class="row">
                <div class="col-md-8">
                    {% if messages %}
                        {% for message in messages %}
                            <div class="alert alert-{{ message.tags }}">
                                {{ message }}
                            </div>
                        {% endfor %}
                    {% endif %}

                    {% if not request.user.is_superuser and not request.useris_staff %}
                        <div class="account-heading">
                            <h2>
                                Performance Calculator
                            </h2>
                        </div>

                        <div class="content-section">
                            <form method="POST">
                                {% csrf_token %}
                                <fieldset class="form-group">
                                    <legend class="border-bottom mb-4"></legend>
                                    {{ performance_form|crispy }}
                                </fieldset>
                                <div class="from-group">
                                    <button class="btn btn-outline-info" type="submit">Calculate</button>
                                </div>
                            </form>
                        </div>
                    {% endif %}
                </div>                
            </div>
        </main>

        <!-- Optional JavaScript -->
        <!-- jQuery first, then Popper.js, then Bootstrap JS -->
        <script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
        <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
        <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
    </body>
</html>

我在语句skype = Detail.objects.filter(subject__subject=sub, user__username=User.username).get('skype_session_attendance')上遇到的全部错误是：

ValueError at /esacp/performance-calculator/
too many values to unpack (expected 2)
Request Method: POST
Request URL:    http://localhost:8000/esacp/performance-calculator/
Django Version: 3.0.3
Exception Type: ValueError
Exception Value:    
too many values to unpack (expected 2)
Exception Location: C:\environments\bsse_fyp\lib\site-packages\django\db\models\sql\query.py in build_filter, line 1247
Python Executable:  C:\environments\bsse_fyp\Scripts\python.exe
Python Version: 3.8.1
Python Path:    
['C:\\Users\\khubi\\OneDrive\\Desktop\\FYP\\test_phase',
 'C:\\Users\\khubi\\AppData\\Local\\Programs\\Python\\Python38-32\\python38.zip',
 'C:\\Users\\khubi\\AppData\\Local\\Programs\\Python\\Python38-32\\DLLs',
 'C:\\Users\\khubi\\AppData\\Local\\Programs\\Python\\Python38-32\\lib',
 'C:\\Users\\khubi\\AppData\\Local\\Programs\\Python\\Python38-32',
 'C:\\environments\\bsse_fyp',
 'C:\\environments\\bsse_fyp\\lib\\site-packages']
Server time:    Thu, 14 May 2020 07:12:19 +0000

我不知道出什么问题了，为什么会显示此错误。我在这里阅读了与相同问题相关的其他线程，但是他们的问题是他们使用的是2D元组而不是1D元组，或者有时是字典或列表问题，但我没有任何问题。

我花了数小时来寻找问题，但找不到。非常感谢您的帮助。

python django valueerror
1个回答
0
投票
skype = Detail.objects.filter(...).values().first().get('skype_session_attendance')

您正在调用get实例的QuerySet方法。如果结果为None或存在多个实例，则需要kwargs并返回一个实例，否则将引发错误。要获取Skype值，您必须首先获取实例。

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