[Python-Dev] Incorrect behavior in str.format() method when padding with '\x00'

[Eric V. Smith]

On 04/03/2014 11:49 AM, MRAB wrote:
> On 2014-04-03 16:20, Eric V. Smith wrote:
>> On 04/02/2014 04:08 PM, John Tyree wrote:
>>>
>>> Hi all,
>>>
>>> Is there any particularly reason for the following behavior on both
>>> 2.7.6 and 3.4.0 ?
>>>
>>>     >>> "{:\x00<5}".format(2)
>>>     '2    '
>>>     >>>
>>>     "{:\x20<5}".format(2)
>>>
>>>     '2    '
>>>     >>>
>>>     "{:\x01<5}".format(2)
>>>
>>>     '2\x01\x01\x01\x01'
>>>     >>> "{:\x00<5}".format(2) ==
>>>     "{:\x20<5}".format(2)
>>>
>>>     True
>>>
>>>
>>> The docs say "If a valid /align/ value is specified, it can be preceded
>>> by a /fill/ character that can be any character and defaults to a space
>>> if omitted," so I'm inclined to call this a good old fashioned bug.
>>
>> I'd say it's a bug. Please open a bug, assign it to me (eric.smith), and
>> I'll comment on it there.
>>
> I'd agree. It looks like '\x00' is being confused with a NUL terminator
> in the C code. I've seen such a thing before (now fixed).

Now that I recall the other issue (that I should have fixed already, but
let drop), it's because 0 is used as a flag to mean "use the default".

Eric.