python - 列表索引超出范围(使用 json)

Question

我导入了 json 并按名称过滤它。

def lootprice(json_object, name):
    needobj = [obj for obj in json_object if obj['name'] == name][0]
    if needobj['have'] < needobj['max']:
        return needobj['price']

它工作了一段时间，然后显示这种错误:

needobj = [obj for obj in json_object if obj['name'] == name][0] 

IndexError: list index out of range

Answer 1

[obj for obj in json_object if obj['name'] == name] 返回空，这意味着 json_object 中没有搜索到的名称。您应该捕获该异常并相应地返回一些内容。

def lootprice(json_object, name):
    try:
        needobj = [obj for obj in json_object if obj['name'] == name][0]
    except IndexError:
        # Return something that tells the user no results where found
        return None
    if needobj['have'] < needobj['max']:
        return needobj['price']

完整示例在这里:

def lootprice(json_object, name):
    try:
        needobj = [obj for obj in json_object if obj['name'] == name][0]
    except IndexError:
        return None
    if needobj['have'] < needobj['max']:
        return needobj['price']

my_object = [
    {'obj_id': 1, 'name': 'test1', 'have': 12, 'max': 50, 'price': 11},
    {'obj_id': 2, 'name': 'test2', 'have': 12, 'max': 50, 'price': 22},
    {'obj_id': 4, 'name': 'test4', 'have': 12, 'max': 50, 'price': 44},
    {'obj_id': 5, 'name': 'test5', 'have': 12, 'max': 50, 'price': 55}
]

lootprice(my_object, 'test1') # Returns 11
lootprice(my_object, 'test2') # Returns 22
lootprice(my_object, 'test3') # Returns None
lootprice(my_object, 'test4') # Returns 44
lootprice(my_object, 'test5') # Returns 55