| msg78356 - (view) |
Author: STINNER Victor (vstinner) *  |
Date: 2008-12-27 12:58 |
| Python 2.x allows to encode any byte string (str) and ASCII unicode string (unicode): $ python Python 2.5.1 (r251:54863, Jul 31 2008, 23:17:40) >>> import zlib >>> zlib.compress('abc') "x\x9cKLJ\x06\x00\x02M\x01'" >>> zlib.compress(u'abc') "x\x9cKLJ\x06\x00\x02M\x01'" >>> zlib.compress(u'abc\xe9') ... UnicodeEncodeError: 'ascii' codec can't encode character u'\xe9' ... I'm not sure that this behaviour was really wanted become the decompress operation is not symetric (the result type is always byte string): $ python Python 2.5.1 (r251:54863, Jul 31 2008, 23:17:40) >>> import zlib >>> zlib.decompress("x\x9cKLJ\x06\x00\x02M\x01'") 'abc' --- Python 3.0 accepts any string: bytes or characters. But decompress always produce bytes string: $ ./python Python 3.1a0 (py3k:67926M, Dec 26 2008, 23:59:07) >>> import zlib >>> zlib.compress(b'abc') b"x\x9cKLJ\x06\x00\x02M\x01'" >>> zlib.compress('abc') b"x\x9cKLJ\x06\x00\x02M\x01'" >>> zlib.compress('abc\xe9') b'x\x9cKLJ>\xbc\x12\x00\x06\xca\x02\x93' >>> zlib.compress('abc\xe9'.encode('utf-8')) b'x\x9cKLJ>\xbc\x12\x00\x06\xca\x02\x93' >>> zlib.decompress(b'x\x9cKLJ>\xbc\x12\x00\x06\xca\x02\x93') b'abc\xc3\xa9' The most strange operation is the decompression of an unicode string: $ ./python >>> zlib.decompress('x\x9cKLJ>\xbc\x12\x00\x06\xca\x02\x93') ... zlib.error: Error -3 while decompressing data: incorrect header check --- I propose to change zlib API to reject unicode string and use explicit conversion to/from bytes. Functions/methods: - compress(bytes, ...) - decompress(bytes, ...) - .compress(bytes, ...) - .decompress(bytes, ...) - crc32(bytes, value=0) - adler(bytes, value=1) Note: binascii.crc32() already rejects unicode string. The behaviour may kept in Python 3.0.x and only changed in Python 3.1. |
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| msg78357 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2008-12-27 13:00 |
| See also issue #4738 (better threads support in zlib). |
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| msg78360 - (view) |
Author: Marc-Andre Lemburg (lemburg) * |
Date: 2008-12-27 13:13 |
| On 2008-12-27 13:58, STINNER Victor wrote: > Python 2.x allows to encode any byte string (str) and ASCII unicode > string (unicode): > > $ python > Python 2.5.1 (r251:54863, Jul 31 2008, 23:17:40) >>>> import zlib >>>> zlib.compress('abc') > "x\x9cKLJ\x06\x00\x02M\x01'" >>>> zlib.compress(u'abc') > "x\x9cKLJ\x06\x00\x02M\x01'" >>>> zlib.compress(u'abc\xe9') > ... > UnicodeEncodeError: 'ascii' codec can't encode character u'\xe9' ... > > I'm not sure that this behaviour was really wanted become the > decompress operation is not symetric (the result type is always byte > string): > > $ python > Python 2.5.1 (r251:54863, Jul 31 2008, 23:17:40) >>>> import zlib >>>> zlib.decompress("x\x9cKLJ\x06\x00\x02M\x01'") > 'abc' > I don't see a problem with this. The fact that Python 2.x also accepts Unicode ASCII strings where strings are normally expected is intended to help with the migration to Unicode, so the above is expected. zlib itself doesn't care about whether the data to be encoded is text or bytes. In Python 3.x, it's probably better to use bytes throughout the API. |
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| msg78365 - (view) |
Author: Lukas Lueg (ebfe) |
Date: 2008-12-27 13:58 |
| I don't think Python 2.x should be changed - but 3.0 or 3.1 should be: - Characters don't mean a thing in zlib-land, all operations are based on bytes and their (implicit) default encoding. This behaviour is hidden and somewhat violates the rule of least surprise. - type(zlib.decompress(zlib.compress('abc'))) == bytes anyway - Changing from s* to y* forces the programmer to use .encode() on his strings (e.g. zlib.compress('abc'.encode()) which very clearly shows what's happening. If you want to compress and decompress Python3 strings, you *must* share the same character encoding; think of zlib.compress('hôńè') and str(zlib.decompress(x)) with different locales. - Other modules (hashlib comes to my mind...) already reject Unicode objects for the same argument. |
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| msg79090 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2009-01-04 22:51 |
| > The fact that Python 2.x also accepts Unicode ASCII strings > where strings are normally expected is intended to help with > the migration to Unicode I hate this behaviour. It doesn't help migration, it's the opposite! Sometimes it works (ASCII), and somtimes it fails (just one non-ASCII character). And then we will read "Unicode sucks!" because people doesn't understand the error. > In Python 3.x, it's probably better to use bytes throughout the > API. I propose to reject unicode in Python 3.x and display a warning for Python 2.x. A warning to prepare the migration... not to Unicode, but to Python3 ;-) |
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| msg79110 - (view) |
Author: Lukas Lueg (ebfe) |
Date: 2009-01-05 06:44 |
| The current behaviour may help the majority by ignorance and cause weird errors for others. We tell people that Python distincts between Text and Data but actually treat it all the same by implicit encoding. Modules that only operate on Bytes should reject Unicode-objects in Python3; it's a matter of 3 lines to display a warning in Python 2. Those modules that usually operate on Text but have single functions that operate on Bytes should display a warning but not enforce explicit encoding. Also see #4821 and #4818 where unicode already got rejected by the openssl-driven classes but silently accepted by the build-in ones. |
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| msg79124 - (view) |
Author: Marc-Andre Lemburg (lemburg) * |
Date: 2009-01-05 10:44 |
| On 2009-01-04 23:51, STINNER Victor wrote: > STINNER Victor <victor.stinner@haypocalc.com> added the comment: > >> The fact that Python 2.x also accepts Unicode ASCII strings >> where strings are normally expected is intended to help with >> the migration to Unicode > > I hate this behaviour. It doesn't help migration, it's the opposite! Sometimes > it works (ASCII), and somtimes it fails (just one non-ASCII character). And > then we will read "Unicode sucks!" because people doesn't understand the > error. Well, that's your opinion. The feature was added to get people work with Unicode at all, since otherwise we would have had to do all the Unicode porting we're doing now for Python 3 at the time Unicode was introduced - which was in version Python 1.6, eight years ago. At the time the Python community was a lot smaller and there wasn't all that much interest in Unicode anyway - the Unicode support I wrote for Python 1.6 was partially financed by HP which needed it for an application they had written in Python. See the introduction in PEP 100 for the motivation behind the design decisions: http://www.python.org/dev/peps/pep-0100/ >> In Python 3.x, it's probably better to use bytes throughout the >> API. > > I propose to reject unicode in Python 3.x and display a warning for Python > 2.x. A warning to prepare the migration... not to Unicode, but to Python3 ;-) Fair enough. |
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| msg79225 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2009-01-06 01:38 |
| > > I propose to reject unicode in Python 3.x and display a warning for > > Python 2.x. A warning to prepare the migration... not to Unicode, but to > > Python3 ;-) > > Fair enough. The patch for Python 3.x is already attached to this issue. We might only apply this one and leave Python 2.x unchanged. Can someone review the patch? |
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| msg96376 - (view) |
Author: Florent Xicluna (flox) * |
Date: 2009-12-14 13:55 |
| Definitely, zlib.compress should raise a TypeError (like bz2 does). >>> import bz2, zlib >>> bz2.compress('abc') Traceback (most recent call last): File "", line 1, in TypeError: argument 1 must be bytes or buffer, not str >>> zlib.compress('abc') b"x\x9cKLJ\x06\x00\x02M\x01'" Someone can review the patch and merge it? |
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| msg96378 - (view) |
Author: Antoine Pitrou (pitrou) * |
Date: 2009-12-14 15:05 |
| The patch lacks a test that TypeError is raised on unicode input, otherwise it's fine. |
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| msg96382 - (view) |
Author: Florent Xicluna (flox) * |
Date: 2009-12-14 16:35 |
| Patch from haypo updated for r76830 . Additional tests for TypeError, and to check that bytearray objects are accepted. |
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| msg96383 - (view) |
Author: Antoine Pitrou (pitrou) * |
Date: 2009-12-14 16:55 |
| The patch produces a number of errors in test_tarfile, test_distutils, test_gzip and test_xmlrpc. |
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| msg96384 - (view) |
Author: Florent Xicluna (flox) * |
Date: 2009-12-14 17:04 |
| Fixed. And some "bytearray" tests improved in test_zlib. |
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| msg96389 - (view) |
Author: Antoine Pitrou (pitrou) * |
Date: 2009-12-14 18:24 |
| The patch was committed to py3k and 3.1. Thank you! |
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| msg97491 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2010-01-10 02:31 |
| > The patch was committed to py3k and 3.1. Thank you! r76836 and r76838 |
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