access attribute from another class in python-CodePudding

I'm new in python and try to solve this problme.I apologize if I am not realy good in English. for thid issue I shuldn't change the argument of methods except dunder call.I only brought the part of the code that I had a problem with. I try to use attribute of Passenger class(self.load_weight) in Trip class. but I get error (TypeError: unsupported operand type(s) for -=: 'int' and 'Trip').how can I print the answer without any error?

class Train:
    def __init__(self, weight_capacity):
        self.weight_capacity = weight_capacity


class Trip:
    def __init__(self, train):
        self.train = self.train_validation(train))

    def train_validation(self, train):
        self.train = train
        return self.train

    def __call__(self):
        self.trip = Passenger(self)
        self.train.weight_capacity -= self.trip.load_weight
        return self.train.weight_capacity

class Passenger:

    def __init__(self , load_weight):
        self.load_weight = load_weight

    def attend_trip(self, trip):
        self.trip = trip
    
train = Train(34286)
trip = Trip(train)
passenger1 = Passenger(616)
print(trip())

CodePudding user response：

The problem with your code is that in the line self.trip = Passenger(self) use pass the Train object as an argument. Maybe it's an mistype, because in the Passenger class you named the variable load_weight. So I am assuming you should pass some kind of number instead of class object.

CodePudding user response：

The reason why your code is not working as expected is because inside the call dunder method of Trip class, you are instancing a new Passenger class instance, instead of using the passenger class instanced below; plus the fact that you are creating the passenger instance itself after the Trip instance (the last 3 lines),

I've done a small refactor of you code, with the suggested modifications:

class Train:
    def __init__(self, weight_capacity):
        self.weight_capacity = weight_capacity


class Trip:
    def __init__(self, train):
        self.train = self.train_validation(train)
        
    def train_validation(self, train):
        self.train = train
        return self.train
    
    def __call__(self, passenger):
        self.trip = passenger
        self.train.weight_capacity -= self.trip.load_weight
        return self.train.weight_capacity


class Passenger:
    
    def __init__(self, load_weight):
        self.load_weight = load_weight
    
    def attend_trip(self, trip):
        self.trip = trip


train = Train(34286)
passenger1 = Passenger(616)
trip = Trip(train)
print(trip(passenger1))