如何在 Try/Catch Block Python 中捕获所有异常？

Question

我正在编写 python 代码来在 linux 环境中安装我的程序所需的所有库包。所以 linux 可能包含 python 2.7 或 2.6 或两者，所以我开发了一个 try and except 块代码，它将安装 pip 包linux。 Try 块代码由 python 2.7 版本 pip install 组成，Catch 块包含 python 2.6 版本 pip install。我的问题是代码的和平工作正常，当我尝试在 python 2.6 中安装熊猫时，它给了我一些错误。我想抓住那个异常。你能告诉我如何改进我的 try except 块以捕获该异常

required_libraries = ['pytz','requests','pandas']
try:
   from subprocess import check_output
   pip27_path = subprocess.check_output(['sudo','find','/','-name','pip2.7'])
   lib_installs = [subprocess.call((['sudo',pip27_path.replace('\n',''),'install', i])) for i in required_libraries]
except:
   p = subprocess.Popen(['sudo','find','/','-name','pip2.6'], stdout=subprocess.PIPE);pip26_path, err = p.communicate()
   lib_installs = [subprocess.call((['sudo',pip26_path.replace('\n',''),'install', i])) for i in required_libraries]

Answer 1

您可以使用一个块捕获多个异常。让我们使用 Exception 和 ArithmeticError 来处理异常。

try:
    # Do something
    print(q)

# Catch exceptions  
except (Exception, ArithmeticError) as e:
    template = "An exception of type {0} occurred. Arguments:\n{1!r}"
    message = template.format(type(e).__name__, e.args)
    print (message)

如果您需要捕获多个异常并单独处理每个异常，那么您应该为每个异常编写一个 except 语句。

try:
    # Do something
    print(q)

# Catch exceptions  
except Exception as e:
    print (1)

except ArithmeticError as e:
    print (2)

# Code to be executed if the try clause succeeded with no errors or no return/continue/break statement

else:
    print (3)

您还可以检查异常是否属于“MyCustomException”类型，例如使用 if 语句。

if isinstance(e, MyCustomException):
    # Do something
    print(1)

至于你的问题，我建议将代码分成两个函数。

install(required_libraries)

def install(required_libraries, version='pip2.7'):
    # Perform installation
    try:
        from subprocess import check_output
        pip27_path = subprocess.check_output(['sudo','find','/','-name', version])
        lib_installs = [subprocess.call((['sudo',pip27_path.replace('\n',''),'install', i])) for i in required_libraries]

    except Exception as e:
        backup(required_libraries)

def backup(required_libraries, version='pip2.6'):
    try:
        p = subprocess.Popen(['sudo','find','/','-name',version]], stdout=subprocess.PIPE);pip26_path, err = p.communicate()
        lib_installs = [subprocess.call((['sudo',pip26_path.replace('\n',''),'install', i])) for i in required_libraries]

    except Exception as e:
        template = "An exception of type {0} occurred. Arguments:\n{1!r}"
        message = template.format(type(e).__name__, e.args)
        print (message)

        #Handle exception

注意：我没有对此进行测试，我也不是专家，所以希望能提供帮助。

有用的链接：

1. Built-in Exceptions
2. Errors and Exceptions
3. Compound statements