我可以从python的finally块中得到异常吗？

Question

我的脚本中有try/finally子句。是否可以从finally子句中得到确切的错误信息？

Answer 1

不，在finally时间sys.exc_info是全没有，是否有异常 与否。用途：

try: 
    whatever 
except: 
    here sys.exc_info is valid 
    to re-raise the exception, use a bare `raise` 
else: 
    here you know there was no exception 
finally: 
    and here you can do exception-independent finalization 

Answer 2

你会想要在except子句中这样做，而不是finally中。

参考：http://www.doughellmann.com/articles/Python-Exception-Handling/

Answer 3

的finally块将被无论一个异常是否抛出，或不执行，从而乔希指出的，你很可能不希望在那里处理它。

如果您确实需要引发异常的值，那么您应该在except块中捕获异常，并对其进行适当处理或重新提升，然后在finally块中使用该值 - - 如果在执行过程中没有发生异常情况，我们期望它可能从未设置过。

import sys 

exception_name = exception_value = None 

try: 
    # do stuff 
except Exception, e: 
    exception_name, exception_value = sys.exc_info()[:2] 
    raise # or don't -- it's up to you 
finally: 
    # do something with exception_name and exception_value 
    # but remember that they might still be none 

Answer 4

其实，其他答案有点模糊。所以，让我澄清一下。你总是可以从finally块中调用sys.exc_info（）。但是，它的输出会根据异常是否实际发生而变化。

import sys 

def f(i): 

    try: 
     if i == 1: 
      raise Exception 
    except Exception as e: 
     print "except -> " + str(sys.exc_info()) 
    finally: 
     print "finally -> " + str(sys.exc_info()) 

f(0) 
f(1) 

>>> 
finally -> (None, None, None) 
except -> (<type 'exceptions.Exception'>, Exception(), <traceback object at 0x029438F0>) 
finally -> (<type 'exceptions.Exception'>, Exception(), <traceback object at 0x029438F0>) 

因此，如果是第一级函数，则可以在finally块中始终知道是否引发异常。但是当调用堆栈的长度超过1时，sys.exc_info（）的行为会有所不同，如下例所示。欲了解更多信息，请参考How sys.exc_info() works?

import sys 

def f(i): 

    try: 
     if i == 1: 
      raise Exception 
    except Exception as e: 
     print "except -> " + str(sys.exc_info()) 
    finally: 
     print "finally -> " + str(sys.exc_info()) 

def f1(i): 
    if i == 0: 
     try: 
      raise Exception('abc') 
     except Exception as e: 
      pass 

    f(i) 

f1(0) 
f1(1) 

>>> 
finally -> (<type 'exceptions.Exception'>, Exception('abc',), <traceback object at 0x02A33940>) 
except -> (<type 'exceptions.Exception'>, Exception(), <traceback object at 0x02A33990>) 
finally -> (<type 'exceptions.Exception'>, Exception(), <traceback object at 0x02A33990>) 

我希望，它使事情更清晰。

Answer 5

前tryexcept块就定义可能是个例外空白变量：

import sys 

exception = None 

try: 
    result = 1/0 
except ZeroDivisionError as e: 
    exception = sys.exc_info() # or "e" 
finally: 
    if exception: 
     print(exception) 
    else: 
     print('Everything is fine') 

测试上的Python 3.6