Calling an instance variable in another class

Question

I am trying to access the instance variable self.code in class Line in class Quote. I am trying to make the following rule pass: when a quote is made containing both a 'door_sign' and 'escape_sign' line they receive 10% off the entire quote.

Here's the code.

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):

**** Here is where my problem lies ****

    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

Looks like you are always giving a discount since escape_sign is always True and computing the cost incorrectly by returning early. Why don't you try this in the def cost method:

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

Quick edit , I missed that you want the discount if both escape_sign and door_sign are in the order.

If you want it in one loop:

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

Answer 2

class Quote:
    def __init__(self, client=None, lines=[]):
        self.client = client
        self.lines = lines
    def cost(self):
        codes={l.code for l in self.lines}
        price_modifier = 0.9 if codes.issuperset({'door_sign','escape_sign'}) else 1.0
        return sum([l.cost()*price_modifier for l in self.lines])