如何修改Python调用代码使出错的外部脚本终止主程序？

问题背景 #

我们有一个Python 3面向对象程序，需要调用第三方提供的外部脚本。当前问题是：当被调用的脚本返回非零退出码（执行出错）时，主程序仍会继续运行，而非报错终止。由于无法控制第三方脚本的内容，必须在主程序中添加错误处理逻辑。

复现步骤 #

• 创建两个目录MyApp和AnotherDir，文件结构如下：

  AnotherDir\scripts\brokenScript.py
  MyApp\app\main.py
  MyApp\app\second_level.py
  MyApp\app\third_level.py
  

• 导航到两个目录的父目录
• 执行命令：

  python MyApp\app\main.py
  

当前结果 #

About to run a broken script that should break on error.
command is:  python C:\path\to\AnotherDir\scripts\brokenScript.py
shell Inside broken script.  The script should break on the next line.
----------------------------------------------------------------------------
FAILED TO THROW ERROR. Done running the broken script, but it returned without breaking this calling program.  This print command should never run if the script breaks.  Instead, a graceful error message should terminate the program.

期望结果 #

当brokenScript.py返回非零退出码时，主程序应捕获该错误并终止运行，而非继续执行后续代码。

解决方案：修改以下代码实现错误捕获与终止 #

1. 修改third_level.py中的runShellCommand函数 #

当前subprocess.Popen启动进程后，未检查进程的退出状态码。需在读取完输出后，获取返回码并判断是否为非零，若为非零则抛出异常：

def runShellCommand(self, commandToRun):
    proc = subprocess.Popen(commandToRun, cwd=None, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, shell=True)
    while True:
        line = proc.stdout.readline()
        if line:
            thetext = line.decode('utf-8').rstrip('\r|\n')
            decodedline = self.ansi_escape.sub('', thetext)
            logString = decodedline
            print("shell", logString)
        else:
            break
    # 新增：等待进程结束并检查退出码
    proc.wait()
    exit_code = proc.returncode
    if exit_code != 0:
        raise subprocess.CalledProcessError(exit_code, commandToRun)

2. 修改third_level.py中的runScript函数 #

调用runShellCommand时捕获异常，输出错误信息后终止程序：

def runScript(self, relativePathToScript):
    userCallingDir = str(os.path.abspath("."))+'\\'
    userCallingDir = self.formatPathForOS(userCallingDir)
    fullyQualifiedPathToScript = userCallingDir+relativePathToScript
    fullyQualifiedPathToScript = self.formatPathForOS(fullyQualifiedPathToScript)
    if os.path.isfile(fullyQualifiedPathToScript):
        commandToRun = "python "+fullyQualifiedPathToScript
        print("command is: ",commandToRun)
        try:
            self.runShellCommand(commandToRun)
        except subprocess.CalledProcessError as e:
            print(f"shell ERROR: 脚本执行失败，退出码 {e.returncode}")
            sys.exit(1)
    else: 
        logString = "ERROR: "+fullyQualifiedPathToScript+" is not a valid path. "
        print('shell', logString)
        sys.exit(1)

3. （可选）优化second_level.py的错误处理 #

如果需要在业务层添加额外提示，可修改offFoundation函数捕获终止信号：

def offFoundation(self):
    tl = third_level()
    print("About to run a broken script that should break on error.")
    callScript = "\\AnotherDir\\scripts\\brokenScript.py"
    try:
        tl.runScript(callScript)
    except SystemExit:
        print("程序因外部脚本执行失败而终止")
        raise
    # 以下代码仅在脚本执行成功时运行
    print("----------------------------------------------------------------------------")
    print("脚本执行成功完成")

内容的提问来源于stack exchange，提问作者CodeMed