请我是 python 的新手，我正在尝试使用 Django 做一个食谱应用程序。 我遇到了一个错误，即“UnboundLocalError：局部变量形式

Question

this is the picture of my views.py

When I ran the code I saw an this error in the browser UnboundLocalError: local variable 'form' referenced before assignment

Answer 1

you only create form if your request is POST. so if you try to call your view with get method form variable is not created.

---

this is your code I'm gonna walk you through it.

def register(request):
    if request.method == "POST":
        form = UserCreationForm(request.POST)
        if form.is_valid():
            username = form.cleaned_data.get('username')
            messages.success(request,f"{username}, your account has been created!")
            return redirect('recipes-home')
        else:
            form = UserCreationForm()
    return render(request,'users/Register.html',{'form',form})

if a user post something to your register view this happens: they go in this condition:

form = UserCreationForm(request.POST)
if form.is_valid():
    username = form.cleaned_data.get('username')
    messages.success(request,f"{username}, your account has been created!")
    return redirect('recipes-home')
else:
    form = UserCreationForm()

if data is valid they get redirected. else an empty form is created and then this line:

return render(request,'users/Register.html',{'form',form})

works because it's out of if condition and an empty form exists. but if a user tries to request the view with get method this code executes because condition checks for "POST":

def register(request):
    return render(request,'users/Register.html',{'form',form})

so now you can see that your code can't understand where did the form came from.

you can use this to make your code work.

def register(request):
    if request.method == "POST":
        form = UserCreationForm(request.POST)
        if form.is_valid():
            username = form.cleaned_data.get('username')
            messages.success(request,f"{username}, your account has been created!")
            return redirect('recipes-home')
        else:
            form = UserCreationForm()
    if request.method == "GET":
        form = UserCreationForm()
    return render(request,'users/Register.html',{'form',form})