python - 调用另一个类中的实例变量

Question

我正在尝试访问类 Quote 中的类 Line 中的实例变量 self.code 。我试图让以下规则通过:当报价包含“door_sign”和“escape_sign”行时，他们将获得整个报价 10% 的折扣。

这是代码。

class Client:
    def __init__(self, postcode):
        self.postcode = postcode


class Line:
    def __init__(self, code, unit_cost, quantity=1):
        self.code = code
        self.unit_cost = unit_cost
        self.quantity = quantity

    def cost(self):

        if self.code == 'door_sign' and self.quantity >=3:
            return self.unit_cost * self.quantity * 0.8
        else:
            return self.unit_cost * self.quantity

class Quote:
    def __init__(self, client=None, lines=[]):
        self.client = client
        self.lines = lines

    def cost(self):

**** 这就是我的问题所在 ****

    for l in self.lines:
        if line.code == 'door_sign' and 'escape_sign':
            return sum([l.cost() * 0.9])
        else:
            return sum([l.cost()])

print('Rule')
assert Quote(client=Client(postcode=3000), lines=[
Line(code='escape_sign', unit_cost=20.0, quantity=10),
]).cost() == 200.0
assert Quote(client=Client(postcode=3000), lines=[
Line(code='door_sign', unit_cost=10.0, quantity=1),
Line(code='escape_sign', unit_cost=20.0, quantity=10),
]).cost() == 189.0

Answer 1

看起来您总是在提供折扣，因为 escape_sign 始终为 True 并且提前返回会错误地计算成本。为什么不在 def cost 方法中尝试一下:

def cost(self):
    needed = {'door_sign', 'escape_sign'}
    discount = {l.code for l in self.lines} & needed == needed
    cost = sum(l.cost() for l in self.lines)
    return (cost * 0.9) if discount else cost

快速编辑，我错过了如果escape_sign和door_sign都在订单中，您想要折扣。

如果你想在一个循环中进行:

def cost(self):
    door = False
    escape = False
    cost = 0
    for line in self.lines:
        if line.code == 'escape_sign':
            escape = True
        elif line.code == 'door_sign':
            door = True
        cost += line.cost()
    return (cost * 0.9) if (escape and door) else cost