linux-kernel - Re: [PATCH] selftests/tpm2: Change exception handling to be Python 3 compatible

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Date:   Tue, 14 Apr 2020 07:45:33 +0200
From:   Ezra Buehler <ezra@...yb.ch>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     Shuah Khan <shuah@...nel.org>, linux-kselftest@...r.kernel.org,
        linux-integrity@...r.kernel.org,
        Tadeusz Struk <tadeusz.struk@...el.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] selftests/tpm2: Change exception handling to be Python 3
 compatible

Hi Jarkko,

On 13 Apr 2020, at 20:04, Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com> wrote:
> 
> On Mon, Apr 13, 2020 at 07:02:20AM +0200, Ezra Buehler wrote:
>> Hi Jarkko,
>> 
>> On 12 Apr 2020, at 19:07, Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com> wrote:
>>> 
>>> On Sun, Apr 12, 2020 at 05:02:27PM +0200, Ezra Buehler wrote:
>>>> Hi Jarkkon,
>>>> 
>>>>> On 12 Apr 2020, at 16:36, Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com> wrote:
>>>>> +        except ProtocolError(e):
>>>> 
>>>> Should this not be
>>>> 
>>>>       except ProtocolError as e:
>>> 
>>> Unless there is a functional difference, does it matter?
>>> 
>>> /Jarkko
>> 
>> Well, your patch confuses me a lot. It looks to me like you are passing
>> the undefined `e` variable to the constructor.
>> 
>> When I run flake8 on it I get following error (among others):
>> 
>>    F821 undefined name 'e'
> 
> I don't know what flake8 is.

https://flake8.pycqa.org/en/latest/

>> What I suggested is the standard syntax:
>> https://docs.python.org/3/tutorial/errors.html
> 
> It passed the Python 3 interpreter.

That is because it is technically valid syntax.

>> Did you test this? You should get an error as soon as an exception
>> occurs.
> 
> Yes. Interpreter did not complain. I did not know that the language
> is broken that way that you have to exercise the code path to get
> a syntax error.

That is due to the dynamic nature of Python. You won’t get a syntax
error. You will get an exception:

    NameError: name 'e' is not defined

Python has to assume that `e` might be defined at runtime. However,
style checkers will complain.

> 
> /Jarkko

Cheers,
Ezra.