为何Python代码try块正常执行却触发异常返回False？

我写了一段用于学校项目的Python代码，运行时发现尽管try块里的逻辑看似正常执行，但loadData函数始终会进入except块返回False，导致测试失败。我怀疑是while循环的问题，但不确定具体原因，希望有人帮忙分析。

原代码 #

allAirports = []
allFlights = {}

def loadData(airportFile, flightFile):

    try:
        airFile = open(airportFile, "r")
        fileFlight = open(flightFile, "r")


        while True:

            line = airFile.readline()
            line = line.replace(' ', '')
            line = line.replace('  ', '')
            airList = list(line.split(','))
            airList[-1] = airList[-1].strip()

            if airList[0] == '':
                line1 = fileFlight.readline()
                line1 = line1.replace(' ', '')
                line1 = line1.replace('  ', '')
                line1 = line1.replace('    ', '')
                flightList = list(line1.split(','))
                flightList[-1] = flightList[-1].strip()

                for i in range (1):

                    line2 = getAirportByCode(flightList[1])
                    line2 = line2.replace('(', ' ')
                    line2 = line2.replace(')', ' ')
                    line2 = line2.replace(',', ' ')
                    line2 = line2.split()
                    line2[1] = re.sub(r"([A-Z])", r" \1", line2[1]).lstrip()
                    line2[2] = re.sub(r"([A-Z])", r" \1", line2[2]).lstrip()

                    line3 = getAirportByCode(flightList[2])
                    line3 = line3.replace('(', ' ')
                    line3 = line3.replace(')', ' ')
                    line3 = line3.replace(',', ' ')
                    line3 = line3.split()
                    line3[1] = re.sub(r"([A-Z])", r" \1", line3[1]).lstrip()
                    line3[2] = re.sub(r"([A-Z])", r" \1", line3[2]).lstrip()

                    if flightList[1] in allFlights:
                        allFlights[flightList[1]] += [Flight(flightList[0], Airport(line2[0], line2[1], line2[2]), Airport(line3[0], line3[1], line3[2]))]
                    else:
                        allFlights.setdefault(flightList[1], [])
                        allFlights[flightList[1]] += [Flight(flightList[0], Airport(line2[0], line2[1], line2[2]), Airport(line3[0], line3[1], line3[2]))]
            else:
                allAirports.append(Airport(airList[0], airList[1], airList[2]))
    except:

        return False

def getAirportByCode(code):
    code1 = code
    for i in range (len(allAirports)):
        if code1 in str(allAirports[i]):
            return (str(allAirports[i]).replace(' ', ''))
    return -1

t1 = loadData("airports.txt", "flights.txt")
total = 0
for i in allFlights:
    total += len(allFlights[i])
print(t1)
if t1 and len(allAirports) == 37 and total == 146:
    print("Test 4 Passed. (loadData())")
else:
    print("Test 4 Failed. (loadData())")

问题根源 #

1. 无限循环引发的索引越界错误
   你的while True没有终止条件，当airFile.readline()读到文件末尾时会返回空字符串，此时airList = list(line.split(','))得到['']，触发airList[0] == ''的分支。接着去读fileFlight.readline()，当航班文件也读到末尾时，line1是空字符串，处理后flightList同样是['']，之后调用getAirportByCode(flightList[1])会因为flightList只有一个元素而抛出IndexError，直接触发except块返回False。

2. 缺失的模块导入
   代码里使用了re.sub但没有导入re模块，会抛出ImportError，同样会进入except块。

3. 不可靠的机场匹配逻辑
   getAirportByCode通过把Airport对象转成字符串再匹配代码，这种方式非常脆弱——如果Airport的__str__方法格式变化，匹配就会失效，而且容易出现误匹配。

4. 冗余代码与资源泄漏

   • for i in range(1)完全是多余的，没有实际作用。
   • 打开文件后没有关闭，会造成资源泄漏，最好用with语句管理文件。

修复后的代码 #

import re

allAirports = []
allFlights = {}

# 补全缺失的类定义（原代码里应该有但没贴出来）
class Airport:
    def __init__(self, code, city, country):
        self.code = code
        self.city = city
        self.country = country

class Flight:
    def __init__(self, flight_num, dep_airport, arr_airport):
        self.flight_num = flight_num
        self.dep_airport = dep_airport
        self.arr_airport = arr_airport

def loadData(airportFile, flightFile):
    try:
        # 用with语句自动管理文件，无需手动关闭
        with open(airportFile, "r") as airFile, open(flightFile, "r") as fileFlight:
            # 先读取所有机场数据
            for line in airFile:
                line = line.strip().replace(' ', '')
                if not line:
                    continue
                air_code, city, country = line.split(',')
                allAirports.append(Airport(air_code.strip(), city.strip(), country.strip()))
            
            # 再读取所有航班数据
            for line in fileFlight:
                line = line.strip().replace(' ', '')
                if not line:
                    continue
                flight_num, dep_code, arr_code = line.split(',')
                dep_airport = getAirportByCode(dep_code.strip())
                arr_airport = getAirportByCode(arr_code.strip())
                
                # 跳过无效的机场数据
                if not dep_airport or not arr_airport:
                    continue
                
                # 更新航班字典
                if dep_code in allFlights:
                    allFlights[dep_code].append(Flight(flight_num, dep_airport, arr_airport))
                else:
                    allFlights[dep_code] = [Flight(flight_num, dep_airport, arr_airport)]
        return True
    except Exception as e:
        # 打印错误信息方便调试
        print(f"调试信息: {str(e)}")
        return False

def getAirportByCode(code):
    # 直接对比机场对象的code属性，更可靠
    for airport in allAirports:
        if airport.code == code:
            return airport
    return None

t1 = loadData("airports.txt", "flights.txt")
total = sum(len(flights) for flights in allFlights.values())
print(t1)
if t1 and len(allAirports) == 37 and total == 146:
    print("Test 4 Passed. (loadData())")
else:
    print("Test 4 Failed. (loadData())")

修复说明 #

• 用with语句管理文件，自动关闭，避免资源泄漏。
• 分开读取机场和航班文件，逻辑更清晰，避免混合读取的混乱。
• 重构getAirportByCode，直接对比对象属性，匹配逻辑更可靠。
• 添加异常信息打印，方便调试定位问题。
• 去掉冗余的循环和无效的空格处理，简化代码。
• 补全了原代码缺失的Airport和Flight类定义（原代码里应该存在但未粘贴）。

内容的提问来源于stack exchange，提问作者Kibi Karan