AttributeError:'NoneType'对象没有属性'get'-当我什至有数据并且没有字段为None时如何解决?

问题描述 投票:-1回答:2

我正在创建Django应用。我将编写该系统的简要摘要,然后将共享我的代码。

[当用户(学生)将转到performance_calculator.html时,他/她将看到一个文本框,他/她将必须输入相关的科目名称。输入主题名称后,他/她将单击“计算”按钮,在另一侧(服务器端),将使用输入的名称,系统将搜索该用户(学生)该主题的详细信息(进度)从详细模型中使用主题名称和该用户名作为过滤器。获取进度详细信息后,详细信息中的每个值都将分配给单独的单个变量。这些变量将作为参数传递给fuzz_algo()函数(用于计算性能的模糊逻辑算法),获得结果后,将使用Django消息模块将结果转发至客户端(前端)。

这是摘要,现在当系统尝试获取用户(正在使用系统的学生)的主题(由用户输入名称)的进度详细信息时,我在步骤处收到错误。且错误为AttributeError: 'NoneType' object has no attribute 'get'。我知道当我们从某处收到None并尝试从None中获取某些东西时会发生此错误。但是,我已经使用管理面板填充了详细模型以及主题模型(随附屏幕截图)。我不知道为什么得到None,并且由于None而得到了AttributeError

我的views.py

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).values().first().get('skype_session_attendance')
            internal_course = Detail.objects.filter(subject__subject=sub, user__username=User.username).values().first().get('internal_course_marks')
            prg_lab = Detail.objects.filter(subject__subject=sub, user__username=User.username).values().first().get('programming_lab_activity')
            mid_marks = Detail.objects.filter(subject__subject=sub, user__username=User.username).values().first().get('mid_term_marks')
            final_marks = Detail.objects.filter(subject__subject=sub, user__username=User.username).values().first().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

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

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

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

我的模板(users / performance_calculator.html)

{% if not request.user.is_superuser and not request.user.is_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 %}

这是我得到的完整错误:

AttributeError at /esacp/performance-calculator/
'NoneType' object has no attribute 'get'
Request Method: POST
Request URL:    http://localhost:8000/esacp/performance-calculator/
Django Version: 3.0.3
Exception Type: AttributeError
Exception Value:    
'NoneType' object has no attribute 'get'
Exception Location: C:\Users\khubi\OneDrive\Desktop\FYP\test_phase\users\views.py in performanceCalculator, line 61
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 11:55:41 +0000

现在,下面是管理面板的屏幕快照,其中显示了填充的主题和详细信息模型:这是主要的Django管理面板,请参阅右侧的操作?enter image description here

[这是学科模型,看到添加了4个学科,一个学生2个,其他2个。enter image description here

这是用户(学生)的一个主题的详细模型。请参见输入的详细信息,字段不是None或为空enter image description here

现在我不明白,为什么在没有空白的地方出现错误。

P.S。是的,我以同一用户(学生)登录,其用户详细信息已在上面的屏幕截图中填充。如果您在“模板”中看到,则开始时会显示if condition,如果该用户不是职员而不是超级用户,则仅会显示该表格。因此,很明显,在Django管理面板登录后,我不会看到“性能计算器”表单,只有使用常规帐户登录时,才会看到该表单。但是我仍然遇到错误。

python django attributeerror
2个回答
0
投票

forms.py中,将Meta.model设置为Sub,将Meta.fields设置为['subject']

models.py中,模型Sub没有“主题”属性。


0
投票

澄清:这次查看您的整个代码,您已经将数据插入到数据库中,并且您的表单仅对这些数据执行GET ...因此,出于性能考虑,不应将表单保存(因为每次POST都会创建新对象)。这意味着应该将更好的方法编码为GET而不是POST ...

但是可以说这是一个特例,您想这样做是因为您想...这次我将直接修改您的代码,乍看之下很头疼,因为它查询太多,因此效率很低。

views.py

def performanceCalculator(request):
    if request.method == 'POST':
        performance_form = PerformanceCalculatorForm(request.POST)

        if performance_form.is_valid():
            #performance_form.save() #dont save because you dont need to.
            #just process it by getting the data
            sub = performance_form.cleaned_data['subject']

            detail = Detail.objects.all().filter(user=request.user, subject=sub)
            #get the unique object that matches the filters
            #and I think what is causing you the Nonetype error is your queries
            #(I saw filter(subject__subject=...) and the OneToOneField doesn't 
            #behave the same as a ForeignKey and that may be the case.)

            #now fetch every field into the function
            result = fuzz_algo(detail.skype_session_attendance, detail.internal_course_marks, detail.programming_lab_activity, detail.mid_term_marks, detail.final_term_marks)

            messages.success(request, result) #if it raises int related error, include the str filter later.

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

    context = {
        'performance_form': performance_form
    }

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

编辑:忘记添加此部分

并且在您的models.py中...拥有模型Subject并没有多大意义,因为它具有2个用户关系...

所以更干净的模型是:

#removed the Subject model

class Detail(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    subject = models.CharField(max_length=15) #modified to be a CharField
    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'

#also the Sub class
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