Python新手求助：如何正确获取账户总金额列表的最大值

我是Python新手，在他人协助下编写了账户金额计算代码，现需获取每个账户总金额的最大值。移除max函数相关代码后其余功能正常，但使用max时会触发TypeError: 'int' object is not iterable错误，另一种尝试得到的结果是0。

原代码 #

def inventory(info, months_subscribed, add_free_months, video_on_demand):
    acct_all_total = 0
    acct_max = 0
    # here you init the total value to 0
    if info.get('months_subscribed') == 3:
        months_subscribed_total = info.get('months_subscribed') * 18
    elif info.get('months_subscribed') < 3:
        months_subscribed_total = info['months_subscribed'] * 7
    elif info.get('months_subscribed') > 3:
        months_subscribed_total = info.get('months_subscribed') - 3 * 7 + 18

    print(f"User {info.get('name')} has months subscribed total of : $ {months_subscribed_total} ")

    if info['ad_free_months'] > 0:
        ad_free_total = info.get('ad_free_months') * 2
        print(f" User {info.get('name')} total ad free is : $ {ad_free_total} ")

    if info['video_on_demand'] > 0:
        video_on_demand_total = info.get('video_on_demand') * 27.99

        print(f" User {info.get('name')} total video on demand is $ : {video_on_demand_total} ")

        acct_all_total = int(months_subscribed_total + ad_free_total + video_on_demand_total)
        # acct_all_total = [int(acct_all_total)] 
        print(f"Total for {info.get('name')} is: {acct_all_total} ")

        # acct_max = (max(acct_all_total)) #if I use these hashtag parts I get the type error mentioned above.
    
    # if int(acct_all_total) >  int(acct_all_total):
    #     acct_max = int(acct_all_total)
    #     print(f" User {info.get('name')} max value is: {acct_max} ")

    
    return acct_all_total ; acct_max
    
acct_info = [{'name': 'acct_1', 'months_subscribed': 2, 'ad_free_months': 3, 'video_on_demand': 1},
             {'name': 'acct_2', 'months_subscribed': 1, 'ad_free_months': 2, 'video_on_demand': 2},
             {'name': 'acct_3', 'months_subscribed': 2, 'ad_free_months': 1, 'video_on_demand': 3}]

acct_max = 0
combined_total = 0
months_subscribed = 0
ad_free_months = 0
video_on_demand = 0
months_subscribed_total = 0
ad_free_total = 0
video_on_demand_total = 0
acct_all_total = 0
for acct in acct_info:
    print("--")
    acct_all_total+=inventory(acct, months_subscribed, ad_free_months, video_on_demand)
for acct in acct_info: #when I try it this way I get 0 as a result
    if int(acct_all_total) >  int(acct_all_total):
        acct_max = acct_all_total
         
print("Total for all accounts:",acct_all_total)

原输出示例 #

User acct_1 has months subscribed total of : $ 14 
 User acct_1 total ad free is : $ 6 
 User acct_1 total video on demand is $ : 27.99 
Total for acct_1 is: 47 
--
User acct_2 has months subscribed total of : $ 7 
 User acct_2 total ad free is : $ 4 
 User acct_2 total video on demand is $ : 55.98 
Total for acct_2 is: 66 
--
User acct_3 has months subscribed total of : $ 14 
 User acct_3 total ad free is : $ 2 
 User acct_3 total video on demand is $ : 83.97 
Total for acct_3 is: 99 
Total for all accounts: 212
0

问题分析 #

1. max函数报错原因：acct_all_total是单个整数，不是可迭代的列表，max()函数需要传入列表、元组这类可迭代对象，直接传整数必然触发TypeError。
2. 订阅金额计算错误：第三个分支months_subscribed_total = info.get('months_subscribed') - 3 * 7 + 18运算顺序错误，应该是(info.get('months_subscribed') - 3)*7 + 18，否则会先算3*7，导致结果错误。
3. 函数返回值无效：return acct_all_total ; acct_max在Python中只会返回第一个值acct_all_total，分号无法实现多返回值，正确写法是返回元组return acct_all_total, acct_max。
4. 最大值比较逻辑错误：if int(acct_all_total) > int(acct_all_total)是自己和自己比，永远为False，所以acct_max一直是初始值0。

修正后的代码 #

def inventory(info):
    # 初始化各项金额
    months_subscribed_total = 0
    ad_free_total = 0
    video_on_demand_total = 0
    
    # 计算订阅金额，修正运算顺序
    months = info.get('months_subscribed')
    if months == 3:
        months_subscribed_total = months * 18
    elif months < 3:
        months_subscribed_total = months * 7
    elif months > 3:
        months_subscribed_total = (months - 3) * 7 + 18

    print(f"User {info.get('name')} has months subscribed total of : $ {months_subscribed_total} ")

    # 计算无广告金额
    if info['ad_free_months'] > 0:
        ad_free_total = info.get('ad_free_months') * 2
        print(f" User {info.get('name')} total ad free is : $ {ad_free_total} ")

    # 计算点播金额及账户总金额
    if info['video_on_demand'] > 0:
        video_on_demand_total = info.get('video_on_demand') * 27.99
        print(f" User {info.get('name')} total video on demand is $ : {video_on_demand_total} ")

    # 总金额计算，避免未进入点播分支时变量未定义
    acct_all_total = int(months_subscribed_total + ad_free_total + video_on_demand_total)
    print(f"Total for {info.get('name')} is: {acct_all_total} ")
    
    return acct_all_total
    
acct_info = [{'name': 'acct_1', 'months_subscribed': 2, 'ad_free_months': 3, 'video_on_demand': 1},
             {'name': 'acct_2', 'months_subscribed': 1, 'ad_free_months': 2, 'video_on_demand': 2},
             {'name': 'acct_3', 'months_subscribed': 2, 'ad_free_months': 1, 'video_on_demand': 3}]

combined_total = 0
account_totals = []  # 收集每个账户的总金额

for acct in acct_info:
    print("--")
    total = inventory(acct)
    combined_total += total
    account_totals.append(total)

# 获取最大值
acct_max = max(account_totals)

print("Total for all accounts:", combined_total)
print("Maximum account total:", acct_max)

修正后输出示例 #

--
User acct_1 has months subscribed total of : $ 14 
 User acct_1 total ad free is : $ 6 
 User acct_1 total video on demand is $ : 27.99 
Total for acct_1 is: 47 
--
User acct_2 has months subscribed total of : $ 7 
 User acct_2 total ad free is : $ 4 
 User acct_2 total video on demand is $ : 55.98 
Total for acct_2 is: 66 
--
User acct_3 has months subscribed total of : $ 14 
 User acct_3 total ad free is : $ 2 
 User acct_3 total video on demand is $ : 83.97 
Total for acct_3 is: 99 
Total for all accounts: 212
Maximum account total: 99

内容的提问来源于stack exchange，提问作者Nadia