验证CarForSale是向量空间

from math import isclose
from random import uniform, random, randint
from datetime import datetime, timedelta

def random_time():
    return CarForSale.retrieved_date - timedelta(days=uniform(0,10))

def approx_equal_time(t1, t2):
    test = datetime.now()
    return isclose((test-t1).total_seconds(), (test-t2).total_seconds())

def random_car():
    return CarForSale(randint(1990,2019), randint(0,250000), 
              27000. * random(), random_time())

def approx_equal_car(c1,c2):
    return (isclose(c1.model_year,c2.model_year) 
            and isclose(c1.mileage,c2.mileage) 
            and isclose(c1.price, c2.price)
            and approx_equal_time(c1.posted_datetime, c2.posted_datetime))
    
for i in range(0,100):
    a,b = random_scalar(), random_scalar()
    u,v,w = random_car(), random_car(), random_car()
    test(CarForSale.zero(), approx_equal_car, a,b,u,v,w)