python变量未在函数中更新

Question

class car():
    def __init__(self,make,model,year,fuel_capacity,perkilometer):
        self.make = make
        self.model = model
        self.year = year
        self.fuel_capacity = fuel_capacity
        self.perkilometer = perkilometer

        self.fuel_level = 0

    def fill_tank(self):
        """fills the tank full capacity"""
        self.fuel_level = self.fuel_capacity
        print 'Tank is Full'

    def drive(self):
        """drives untill out of gas"""
        print 'car is moving'
        i = 0

        while 0 <= self.fuel_level:

            self.fuel_level -= self.perkilometer
            print '%s kilometres' % (self.fuel_level-(self.fuel_level-i))
            i+=1

        print 'out of gas'

    def travel(self,kilometer):
        """travels for distance given"""
        self.kilometer = kilometer
        print 'Car is moving'
        i=0

        while 0!=kilometer:
            kilometer-=1

            i+=1

            if self.fuel_level >= self.perkilometer:
                self.fuel_level -= self.perkilometer
                print '%s kilometres' % (kilometer - (kilometer - i))

            elif self.fuel_level < self.perkilometer:
                self.fuel_level=0
                print 'Out of Gas'
                return 0

            elif self.fuel_level == 0:
                print 'Out of Gas'
                return 0

        print 'Reached to destination'

    def continue_driving(self):
        distance_left = self.kilometer - self.fuel_level / self.perkilometer
        leters_needed = distance_left * self.perkilometer

        if distance_left<=self.fuel_level/self.perkilometer:
            print 'Have enough gas to continue'

        else:
            print 'Need %s leter more'% leters_needed


    def update_fuel_level(self,new_level):
        if  new_level <= self.fuel_capacity:
            self.fuel_level = new_level
            print 'Tank has %s leters' % self.fuel_level
        else:
            print "Tank can't hold that much"


    def add_fuel(self,amount):
        """adds fuel to gas tank"""

        if self.fuel_level+amount<=self.fuel_capacity:
            self.fuel_level+=amount
            print 'Added fuel %s leters '%amount

        else:
            print "Tank won't hold that much"

#somehow fuel level is not updating after or in add_fuel func.

my_car = car('hyundai','i20','2016','45',0.083)
my_car.fuel_level = 2
my_car.travel(50)
my_car.add_fuel(1)
my_car.continue_driving()

OUTPUT：

Car is moving
1 kilometres
2 kilometres
3 kilometres
4 kilometres
5 kilometres
6 kilometres
7 kilometres
8 kilometres
9 kilometres
10 kilometres
11 kilometres
12 kilometres
13 kilometres
14 kilometres
15 kilometres
16 kilometres
17 kilometres
18 kilometres
19 kilometres
20 kilometres
21 kilometres
22 kilometres
23 kilometres
24 kilometres
Out of Gas
Added fuel 1 leters 
Need 3.15 leter more

我用python制造了这辆车，但是当我使用continue_driving方法时，似乎fuel_level没有更新找不到错误。

我主要想实现的目标是计算油箱中的汽油是否足够，如果不向油箱添加燃料的话。

如您所见，当我运行此代码时，它说我们需要再增加3.15升，但应该是8.3 / 2-（1 + 2）= 2.15

Answer 1

您没有在追踪行进的距离。

您正在尝试根据已消耗的燃料和每公里的公升计算剩余距离。

distance_left = self.kilometer - self.fuel_level / self.perkilometer

您的代码在使用self.fuel_level来计算distance_left之前将其增加。

my_car.add_fuel(1)   # Increased self.fuel_level
my_car.continue_driving()  # Use self.fuel_level to determine distance_left

我建议您跟踪行驶的距离。

def __init__(self,make,model,year,fuel_capacity,perkilometer):
    self.make = make
    self.model = model
    self.year = year
    self.fuel_capacity = fuel_capacity
    self.perkilometer = perkilometer

    self.fuel_level = 0
    self.distance_traveled = 0

然后每次旅行增加它

if self.fuel_level >= self.perkilometer:
    self.fuel_level -= self.perkilometer
    self.distance_traveled += 1
    print '%s kilometres' % self.distance_traveled