如何捕获Try/Catch块Python中的所有异常？

Question

我正在编写python代码来安装我的程序在linux environment.So中所需的所有库包，linux可能包含python2.7或2.6，或者两者都包含，所以我已经开发了一个尝试代码，除了块代码，这些代码将在linux中安装pip包。尝试块代码由python2.7版本pip安装和Catch块包含python2.6版本pip安装组成。我的问题是代码的安全运行良好，当我试图在python2.6中安装熊猫时，它给我带来了一些错误。我想抓住那个例外。请你告诉我如何改进我的尝试，除了块来捕捉异常。

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。让我们使用异常和ArithmeticError作为异常。

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)

如果您需要捕获几个异常并单独处理每个异常，那么您将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为"MyCustomException“类型，例如使用if语句。

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

至于您的问题，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:我没有测试这个，我也不是专家，所以我希望我能帮上忙。

有用的链接：

1. 内建例外
2. 错误和例外
3. 复合语句