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From: Cleber Rosa <crosa@redhat.com>
To: "Philippe Mathieu-Daudé" <philmd@redhat.com>,
	"Eric Blake" <eblake@redhat.com>,
	"Andrey Shinkevich" <andrey.shinkevich@virtuozzo.com>,
	qemu-devel@nongnu.org, qemu-block@nongnu.org
Cc: kwolf@redhat.com, den@openvz.org, vsementsov@virtuozzo.com,
	Eduardo Habkost <ehabkost@redhat.com>,
	mreitz@redhat.com
Subject: Re: [Qemu-devel] [PATCH] iotests: handle TypeError for Python3 in test 242
Date: Thu, 21 Feb 2019 19:17:56 -0500	[thread overview]
Message-ID: <dbd04ea0-6a60-9817-52b3-a0cc73f1a637@redhat.com> (raw)
In-Reply-To: <4f992059-b448-a234-d319-3eb3bb5e04c9@redhat.com>



On 2/18/19 4:25 PM, Philippe Mathieu-Daudé wrote:
> On 2/18/19 9:05 PM, Eric Blake wrote:
>> [adding Eduardo for some python 2-vs-3 advice]
> 
> And Cleber.
> 
>>
>> On 2/18/19 1:59 PM, Andrey Shinkevich wrote:
>>> To write one byte to disk, Python2 may use 'chr' type.
>>> In Python3, conversion to 'byte' type is required.
>>>
>>> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
>>> ---
>>>  tests/qemu-iotests/242 | 9 +++++++--
>>>  1 file changed, 7 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/tests/qemu-iotests/242 b/tests/qemu-iotests/242
>>> index 16c65ed..6b1f7b8 100755
>>> --- a/tests/qemu-iotests/242
>>> +++ b/tests/qemu-iotests/242
>>> @@ -65,9 +65,14 @@ def toggle_flag(offset):
>>>      with open(disk, "r+b") as f:
>>>          f.seek(offset, 0)
>>>          c = f.read(1)
>>> -        toggled = chr(ord(c) ^ bitmap_flag_unknown)
>>> +        toggled = ord(c) ^ bitmap_flag_unknown
>>>          f.seek(-1, 1)
>>> -        f.write(toggled)
>>> +        try:
>>> +            # python2
>>> +            f.write(chr(toggled))
>>> +        except TypeError:
>>> +            # python3
>>> +            f.write(bytes([toggled]))
>>
>> Looks like it works, but I'm not enough of a python expert to know if
>> there is a more Pythonic elegant approach.
>>

Well, there's no way around the fact that bytes in Python 3 are very
different from bytes in Python 2 (just another name for a string).

What I'd recommend here is to not base the type on the exception, but
choose it depending on the Python version.  Something like:

if sys.version_info.major == 2:
   f.write(chr(toggled))
else:
   f.write(bytes([toggled])]

This is cheaper than raising/catching exceptions, it's self documenting,
and follows the pattern on other tests.

Regards,
- Cleber.

>> If someone else picks it up before my next NBD pull request,
>> Acked-by: Eric Blake <eblake@redhat.com>
>>

  reply	other threads:[~2019-02-22  0:18 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-18 19:59 [Qemu-devel] [PATCH] iotests: handle TypeError for Python3 in test 242 Andrey Shinkevich
2019-02-18 20:05 ` Eric Blake
2019-02-18 21:25   ` Philippe Mathieu-Daudé
2019-02-22  0:17     ` Cleber Rosa [this message]
2019-02-22  9:48       ` Andrey Shinkevich
2019-02-19 10:30 ` Vladimir Sementsov-Ogievskiy

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