bytearray inconsistencies?

Mark Lawrence breamoreboy at yahoo.co.uk
Sat Dec 21 03:31:48 CET 2013


On 21/12/2013 01:58, Ned Batchelder wrote:
> On 12/20/13 8:06 PM, Mark Lawrence wrote:
>> Quoting from http://docs.python.org/3/library/functions.html#bytearray
>>
>> "The bytearray type is a mutable sequence of integers in the range 0 <=
>> x < 256."
>>
>> Quoting from http://docs.python.org/3/library/stdtypes.html#bytes-methods
>>
>> "Whenever a bytes or bytearray method needs to interpret the bytes as
>> characters (e.g. the is...() methods, split(), strip()), the ASCII
>> character set is assumed (text strings use Unicode semantics).
>>
>> Note - Using these ASCII based methods to manipulate binary data that is
>> not stored in an ASCII based format may lead to data corruption.
>>
>> The search operations (in, count(), find(), index(), rfind() and
>> rindex()) all accept both integers in the range 0 to 255 (inclusive) as
>> well as bytes and byte array sequences.
>>
>> Changed in version 3.3: All of the search methods also accept an integer
>> in the range 0 to 255 (inclusive) as their first argument."
>>
>> I don't understand why the docs talk about "a mutable sequence of
>> integers" but then discuss "needs to interpret the bytes as characters".
>
> The split and strip methods work with whitespace when given no
> arguments.  Bytes aren't whitespace.  Characters can be, so the bytes
> need to be interpreted as characters.  Likewise, the is* methods
> (isalnum, isalpha, isdigit, islower, isspace, istitle, isupper) all
> require characters, so the bytes must be interpreted.
>
>>   Further I don't understand why the changes done in 3.3 referred to
>> above haven't also been applied to (say) the split method.  If I can
>> call find to look for a zero, why can't I split on it?
>>
>
> I don't know the reason, but I would guess either no one considered it,
> or it was deemed unlikely to be useful.

Explanation, or lack of it, here http://bugs.python.org/issue12170

>
> If you have a zero, you can split on it with:
> bytestring.split(bytes([0])), but that doesn't explain why find can take
> a simple zero, and split has to take a bytestring with a zero in it.
>

I now have working code as a result of the above paragraph, thanks for 
that :)

-- 
My fellow Pythonistas, ask not what our language can do for you, ask 
what you can do for our language.

Mark Lawrence




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