Some_function()在执行时引发异常,因此程序跳转到异常:

try:
    some_function()
except:
    print("exception happened!")

如何查看导致异常发生的原因?


当前回答

大多数答案指向except(…)as(…):语法(正确),但同时没有人想谈论房间里的大象,而大象是sys.exc_info()函数。 来自sys模块的文档(重点是我的):

This function returns a tuple of three values that give information about the exception that is currently being handled. (…) If no exception is being handled anywhere on the stack, a tuple containing three None values is returned. Otherwise, the values returned are (type, value, traceback). Their meaning is: type gets the type of the exception being handled (a subclass of BaseException); value gets the exception instance (an instance of the exception type); traceback gets a traceback object (see the Reference Manual) which encapsulates the call stack at the point where the exception originally occurred.

我认为sys.exc_info()可以被视为对原始问题“我如何知道发生了什么类型的异常?”的最直接答案。

其他回答

在Python 2中,以下代码很有用

except Exception, exc:

    # This is how you get the type
    excType = exc.__class__.__name__

    # Here we are printing out information about the Exception
    print 'exception type', excType
    print 'exception msg', str(exc)

    # It's easy to reraise an exception with more information added to it
    msg = 'there was a problem with someFunction'
    raise Exception(msg + 'because of %s: %s' % (excType, exc))

实际的异常可以通过以下方式捕获:

try:
    i = 1/0
except Exception as e:
    print e

您可以从Python教程中了解有关异常的更多信息。

这些答案很适合调试,但对于以编程方式测试异常,isinstance(e, SomeException)可能很方便,因为它也测试SomeException的子类,因此您可以创建应用于异常层次结构的功能。

大多数答案指向except(…)as(…):语法(正确),但同时没有人想谈论房间里的大象,而大象是sys.exc_info()函数。 来自sys模块的文档(重点是我的):

This function returns a tuple of three values that give information about the exception that is currently being handled. (…) If no exception is being handled anywhere on the stack, a tuple containing three None values is returned. Otherwise, the values returned are (type, value, traceback). Their meaning is: type gets the type of the exception being handled (a subclass of BaseException); value gets the exception instance (an instance of the exception type); traceback gets a traceback object (see the Reference Manual) which encapsulates the call stack at the point where the exception originally occurred.

我认为sys.exc_info()可以被视为对原始问题“我如何知道发生了什么类型的异常?”的最直接答案。

下面是我处理异常的方式。我们的想法是,如果容易的话,尝试解决问题,然后在可能的情况下添加一个更理想的解决方案。不要在生成异常的代码中解决问题,否则代码会失去原始算法的跟踪,而原始算法应该被准确地编写。但是,传递解决问题所需的数据,并返回一个lambda,以防在生成它的代码之外无法解决问题。

path = 'app.p'

def load():
    if os.path.exists(path):
        try:
            with open(path, 'rb') as file:
                data = file.read()
                inst = pickle.load(data)
        except Exception as e:
            inst = solve(e, 'load app data', easy=lambda: App(), path=path)()
    else:
        inst = App()
    inst.loadWidgets()

# e.g. A solver could search for app data if desc='load app data'
def solve(e, during, easy, **kwargs):
    class_name = e.__class__.__name__
    print(class_name + ': ' + str(e))
    print('\t during: ' + during)
    return easy

目前,由于我不想考虑应用程序的用途,所以我没有添加任何复杂的解决方案。但在未来,当我了解更多可能的解决方案时(因为应用程序设计得更多),我可以添加一个以during为索引的解决方案字典。

在这个例子中,一种解决方案可能是寻找存储在其他地方的应用程序数据,比如‘app.p’文件被错误删除了。

现在,因为编写异常处理程序不是一个明智的想法(我们还不知道解决它的最佳方法,因为应用程序的设计将不断发展),我们只是返回简单的修复,这就像我们第一次运行应用程序一样(在这种情况下)。