＆＃34;从列表或元组创建Decimal时无效的元组大小＆＃34;在DecimalField更新

Question

我有以下型号：

class Invoice(models.Model):
    debt = models.DecimalField(max_digits = 11, decimal_places = 2)

当我尝试更新现有的发票时：

invoice = get_object_or_404(Invoice, pk=invoice_id)
invoice.debt = '0'
invoice.save()

我收到以下错误：

'Invalid tuple size in creation of Decimal from list or tuple. The list or tuple should have exactly three elements.'

我试过

invoice.debt = 0,
invoice.debt = Decimal('0'),
invoice.debt = 0.0,
invoice.debt = Decimal('0.0')

上始终存在相同的错误

invoice.save()

有什么想法吗？ Django 1.10.4，Python 3.4.3，数据库正在使用MySQL 5.5.53-0ubuntu0.14.04.1

Answer 1

你在指定的值之后放了一个逗号，所以Python把它变成了一个元素的元组！

invoice.debt = 0,  # == (0,)
invoice.debt = Decimal('0'),  #  == (Decimal('0'),)
invoice.debt = 0.0,  # == (0.0,)
invoice.debt = Decimal('0.0')