Python初学者运行车辆分类统计代码出现KeyError报错求助

数据老陈

2026-9-25

报错原因与修复方案

核心报错原因

键的大小写不匹配：你在统计计数时调用了cartype.lower()将用户输入的车型编码转为小写后作为字典的键，比如用户输入S，实际存储的键是小写的's'，但你取值时使用的是大写的'S'，字典中没有对应键就触发了KeyError。
未处理缺失键场景：如果没有用户输入过某一类车型，这个类型的键不会被添加到字典中，哪怕大小写匹配，直接取值依然会报错。
额外语法错误：原代码中cartype_count[S]里的S没有加引号，会被Python识别为未定义的变量而非字符串键，会额外触发NameError。

修复后的代码

def cartypes():
    cartype_count = {}
    while True:
        car_name = input("Enter a Car Manufacturer and Model: ")
        cartype = input("What type is it (S)UV, (SE)DAN, (M)INI-VAN, (P)ICK-UP, or (O)THER? ")
        cartype_key = cartype.lower()
        if cartype_key not in cartype_count:
            cartype_count[cartype_key] = 1
        else:
            cartype_count[cartype_key] += 1
        add_or_not = input("Do you want to add more cars (Y/N)? ")
        if add_or_not.lower() == "n":
            break
    
    print("There were", cartype_count.get('s', 0), "SUVs.")
    print("There were", cartype_count.get('se', 0), "SEDANs.")
    print("There were", cartype_count.get('m', 0), "MINI-VANs.")
    print("There were", cartype_count.get('p', 0), "PICK-UPs.")
    print("There were", cartype_count.get('o', 0), "cars that were neither SUVs, SEDANs, MINI-VANs, nor PICKUPs.")

cartypes()