Shopping cart program--python

#-*-coding:utf-8 -*-

goods_list=[(‘Iphone‘,5800),(‘Mac Pro‘,12000),(‘Coffee‘,31),(‘Book‘,81),(‘Bike‘,8000)]
goods_bought=[]
salary=input("please input your salary:")
if salary.isdigit():
    salary=int(salary)
    balance=salary
    while True:
        print("This is our goods list:")
        for index,item in (enumerate(goods_list)):
            print(index,item)
        goods_number=(input("please input goods number you want:"))
        if goods_number.isdigit():
            goods_number=int(goods_number)
            if goods_number>=0 and goods_number<(len(goods_list)):
                if goods_list[goods_number][1]<=balance:
                    goods_bought.append(goods_list[goods_number])
                    balance=balance-goods_list[goods_number][1]%(goods_list[goods_number].balance)
                else:
                    print("Your balance %s is not enough!"%balance)
            else:
                print("The goods number %s is not exist!"%goods_number)
        elif goods_number==‘q‘:
            print("Your goods are:")
            for item in goods_bought:
                print(item)
            print("your balance is:%s"%balance)
            goods_bought.clear()
            exit()
        else:
            print("Your input is wrong!")
else:
    print("your salary is wrong:")