Python人口数据分析程序异常求助：菜单选择逻辑问题排查

我写了个基于Python的人口数据分析小工具，原本设计是通过主菜单让用户选两个功能之一：

• 功能1：统计不同大陆的总人口
• 功能2：计算不同国家的人口变化百分比

但运行起来总有些问题，自己排查半天没头绪，贴出完整代码和样本数据，麻烦各位大佬帮忙看看！

完整代码 #

from collections import Counter
print (30 * '-')
print (" M A I N - M E N U")
print (30 * '-')
print ("Program 1.Total Populations of the different continents")
print ("Program 2.Percentage Change(%) for different countries")
print (30 * '-')
Input1=1
Input2=2
## Get input ###
choice = int(input('Enter your choice [1-2] : '))
### Take action as per selected menu-option ###
while choice==1 or choice==2:
    if (choice == 1):
        counter1 = Counter()
        with open('a.txt') as f:
            for i in range(0,2):
                next(f)
            for line in f:
                splits = line.split(';')
                population = int(splits[3])
                continent = splits[-1].strip()
                counter1[continent] += population
        # Print continents sorted by population
        for continent, pop_sum in counter1.most_common():
            print(continent, ":", pop_sum)
    else:
        counter2 = Counter()
        with open("a.txt") as f:
            for i in range(0,2):
                next(f)
            for line in f:
                splits = line.split(';')
                change = float(splits[6])
                country = splits[1].strip()
                counter2[country] += change
        #Percentage Change By Countries"
        print()
        print ("Percentage Change By Countries")
        for country, change_sum in counter2.most_common():
            print(country, change_sum,"%")

样本数据（a.txt内容） #

World Population Data 2019 from the United Nations
Rank; Country; 2018; 2019; % Share; Pop Change; % Change; Continent
1; China; 1427647786; 1433783686; 18.6; 6135900; 0.43; Asia
2; India; 1352642280; 1366417754; 17.7; 13775474; 1.02; Asia
3; United States of America; 327096265; 329064917; 4.27; 1968652; 0.60; North America
4; Indonesia; 267670543; 270625568; 3.51; 2955025; 1.10; Asia
5; Pakistan; 212228286; 216565318; 2.81; 4337032; 2.04; Asia
6; Brazil; 209469323; 211049527; 2.74; 1580204; 0.75; South America
7; Nigeria; 195874683; 200963599; 2.61; 5088916; 2.60; Africa
8; Bangladesh; 161376708; 163046161; 2.11; 1669453; 1.03; Asia
9; Russian Federation; 145734038; 145872256; 1.89; 138218; 0.09; Europe
10; Mexico; 126190788; 127575529; 1.65; 1384741; 1.10; North America

我总结的核心问题&修复方案 #

1. 最致命的循环逻辑错误 #

原程序的while循环条件是choice==1 or choice==2，但执行完对应功能后，没有重新获取用户输入的步骤，导致程序会无限重复执行同一个功能，完全无法回到主菜单。

2. 缺失输入验证机制 #

如果用户输入非整数（比如字母、符号）或者不在1-2范围内的数字，程序会直接抛出ValueError崩溃。

3. 不必要的工具使用 #

功能2里用Counter完全没必要——样本数据里每个国家只有一条记录，Counter是用来做累加计数的，这里只是赋值存储，用普通字典更合适。

修复后的完整代码 #

我调整了逻辑，解决了上述问题，还加了一些细节优化：

from collections import Counter

def show_main_menu():
    print(30 * '-')
    print(" M A I N - M E N U")
    print(30 * '-')
    print("1. Total Populations of the different continents")
    print("2. Percentage Change(%) for different countries")
    print("3. Exit Program")
    print(30 * '-')

def calculate_continent_total_pop():
    continent_pop = Counter()
    with open('a.txt') as f:
        # 跳过前两行表头，比for循环更简洁
        next(f)
        next(f)
        for line in f:
            line = line.strip()
            if not line:
                continue
            splits = line.split(';')
            # 校验数据格式，避免索引越界
            if len(splits) < 8:
                print(f"跳过格式错误的行: {line}")
                continue
            try:
                pop = int(splits[3].strip())
                continent = splits[-1].strip()
                continent_pop[continent] += pop
            except ValueError:
                print(f"跳过数值错误的行: {line}")
    # 按人口从多到少排序，加千分位分隔符更易读
    print("\n各大陆总人口统计:")
    for continent, total in continent_pop.most_common():
        print(f"{continent}: {total:,}")

def calculate_country_pop_change():
    country_changes = {}
    with open('a.txt') as f:
        next(f)
        next(f)
        for line in f:
            line = line.strip()
            if not line:
                continue
            splits = line.split(';')
            if len(splits) < 8:
                print(f"跳过格式错误的行: {line}")
                continue
            try:
                change_rate = float(splits[6].strip())
                country = splits[1].strip()
                country_changes[country] = change_rate
            except ValueError:
                print(f"跳过数值错误的行: {line}")
    # 按变化率从高到低排序
    print("\n各国人口变化百分比:")
    for country, rate in sorted(country_changes.items(), key=lambda x: x[1], reverse=True):
        print(f"{country}: {rate}%")

# 主循环逻辑
while True:
    show_main_menu()
    try:
        choice = int(input('请输入你的选择 [1-3]: '))
        if choice == 1:
            calculate_continent_total_pop()
        elif choice == 2:
            calculate_country_pop_change()
        elif choice == 3:
            print("程序退出中...")
            break
        else:
            print("无效选项！请输入1-3之间的数字")
    except ValueError:
        print("输入无效！请输入整数")

这个修复版做了这些改进：

• 把菜单和功能拆成独立函数，代码更易维护
• 添加了退出选项，解决了无限循环问题
• 增加输入验证和数据格式校验，避免程序崩溃
• 优化了数字显示格式（千分位分隔符）
• 功能2改用普通字典，更贴合需求

内容的提问来源于stack exchange，提问作者sanjay mc'clough