我经常在其他Stack Overflow问题上看到关于如何不鼓励使用except: pass的评论。这为什么不好呢?有时我不在乎错误是什么,我只想继续写代码。

try:
    something
except:
    pass

为什么使用except: pass块不好?是什么让它变得糟糕?是我传递了一个错误还是我排除了任何错误?


当前回答

In my opinion errors have a reason to appear, that my sound stupid, but thats the way it is. Good programming only raises errors when you have to handle them. Also, as i read some time ago, "the pass-Statement is a Statement that Shows code will be inserted later", so if you want to have an empty except-statement feel free to do so, but for a good program there will be a part missing. because you dont handle the things you should have. Appearing exceptions give you the chance to correct input data or to change your data structure so these exceptions dont occur again (but in most cases (Network-exceptions, General input-exceptions) exceptions indicate that the next parts of the program wont execute well. For example a NetworkException can indicate a broken network-connection and the program cant send/recieve data in the next program steps.

但是只对一个执行块使用pass块是有效的,因为你仍然可以区分不同类型的异常,所以如果你把所有的异常块放在一个中,它就不是空的:

try:
    #code here
except Error1:
    #exception handle1

except Error2:
    #exception handle2
#and so on

可以写成这样:

try:
    #code here
except BaseException as e:
    if isinstance(e, Error1):
        #exception handle1

    elif isinstance(e, Error2):
        #exception handle2

    ...

    else:
        raise

因此,即使是多个带有pass语句的异常块也可能导致代码,其结构处理特殊类型的异常。

其他回答

第一个原因已经说过了——它隐藏了你没有预料到的错误。

(#2)——它使你的代码难以被其他人阅读和理解。如果你捕捉FileNotFoundException当你试图读取一个文件,那么它是相当明显的另一个开发人员'catch'块应该有什么功能。如果您没有指定异常,那么您需要额外的注释来解释该块应该做什么。

(#3) -它演示了惰性编程。如果您使用通用的try/catch,则表明您不了解程序中可能的运行时错误,或者您不知道Python中可能存在哪些异常。捕捉特定的错误表明您了解程序和Python抛出的错误范围。这更有可能使其他开发人员和代码审查人员信任您的工作。

>>> import this

The Zen of Python, by Tim Peters Beautiful is better than ugly. Explicit is better than implicit. Simple is better than complex. Complex is better than complicated. Flat is better than nested. Sparse is better than dense. Readability counts. Special cases aren't special enough to break the rules. Although practicality beats purity. Errors should never pass silently. Unless explicitly silenced. In the face of ambiguity, refuse the temptation to guess. There should be one-- and preferably only one --obvious way to do it. Although that way may not be obvious at first unless you're Dutch. Now is better than never. Although never is often better than right now. If the implementation is hard to explain, it's a bad idea. If the implementation is easy to explain, it may be a good idea. Namespaces are one honking great idea -- let's do more of those!

所以,这是我的观点。每当你发现一个错误,你应该做一些事情来处理它,即把它写在日志文件或其他东西。至少,它告诉您曾经有一个错误。

In my opinion errors have a reason to appear, that my sound stupid, but thats the way it is. Good programming only raises errors when you have to handle them. Also, as i read some time ago, "the pass-Statement is a Statement that Shows code will be inserted later", so if you want to have an empty except-statement feel free to do so, but for a good program there will be a part missing. because you dont handle the things you should have. Appearing exceptions give you the chance to correct input data or to change your data structure so these exceptions dont occur again (but in most cases (Network-exceptions, General input-exceptions) exceptions indicate that the next parts of the program wont execute well. For example a NetworkException can indicate a broken network-connection and the program cant send/recieve data in the next program steps.

但是只对一个执行块使用pass块是有效的,因为你仍然可以区分不同类型的异常,所以如果你把所有的异常块放在一个中,它就不是空的:

try:
    #code here
except Error1:
    #exception handle1

except Error2:
    #exception handle2
#and so on

可以写成这样:

try:
    #code here
except BaseException as e:
    if isinstance(e, Error1):
        #exception handle1

    elif isinstance(e, Error2):
        #exception handle2

    ...

    else:
        raise

因此,即使是多个带有pass语句的异常块也可能导致代码,其结构处理特殊类型的异常。

如果这是糟糕的做法,“通过”就不会是一个选项。 如果你有一个资产,从许多地方接收信息IE一个表单或userInput,它就会派上用场。

variable = False
try:
    if request.form['variable'] == '1':
       variable = True
except:
    pass

我个人更喜欢这个解决方案:

except ValueError as error:
                print(error.args)
                pass

错误。Args给了我一个简单的代码行,它不会太分散人的注意力,但确实有助于代码审查,特别是如果错误有不同的原因,比如

(ValueError('year 0 is out of range'),)
(ValueError('month must be in 1..12'),)
(ValueError('day is out of range for month'),)

当研究熊猫的时间周期时。