python - Django - UnboundLocalError

Question

我在 View 中有一个函数，用于上传 CSV 数据并写入数据库。那部分正在工作。但是，当我尝试检查是否有数据更新或创建时，我收到一条错误消息:

"local variable 'created' referenced before assignment".

View 中的函数如下

def bookings_upload(request):

    prompt = {
        'order': "Please import a valid CSV file"
    }
    if request.method == "GET":
        return render(request, 'booking_app/importBookings.html', prompt)

    csv_file = request.FILES['bookings']

    if not csv_file.name.endswith('.csv'):
        messages.error(request, "This file is not a .csv file.")
        return redirect('/booking_app/bookings_upload/') 

    data_set = csv_file.read().decode('utf-8')
    io_string = io.StringIO(data_set)
    next(io_string)

    for column in csv.reader(io_string, delimiter=',', quotechar="|"):
        _, created = Bookings.objects.update_or_create(
            book_date=column[0],
            grower_number=column[1],
            bales_booked=column[3],
            sale_date=column[6],
            book_id=column[11],
            reoffer=column[12]
        )
    ) 

    if created:
        messages.success(request, "Bookings have been imported successfully")
    else:
        messages.warning(request, "No new bookings were imported. Please check/verify your csv file")   

    context = {}
    return render(request, 'booking_app/importBookings.html', context)

我错过了什么？任何帮助将不胜感激。

Answer 1

@lmiguelvargasf 的回答解释了正在发生的事情，但我认为更好的重构是:

n_created = 0
for column in csv.reader(io_string, delimiter=",", quotechar="|"):
    _, created = Bookings.objects.update_or_create(
        book_date=column[0],
        grower_number=column[1],
        bales_booked=column[3],
        sale_date=column[6],
        book_id=column[11],
        reoffer=column[12],
    )
    if created:
        n_created += 1

if n_created:
    messages.success(request, "%d bookings have been imported successfully" % n_created)
else:
    messages.warning(request, "No new bookings were imported. Please check/verify your csv file")