Hi, First, this is a warning in reST syntax:
System Message: WARNING/2 (pep-0461.txt, line 53) > This area of programming is characterized by a mixture of binary data and > ASCII compatible segments of text (aka ASCII-encoded text). Bringing back a > restricted %-interpolation for ``bytes`` and ``bytearray`` will aid both in > writing new wire format code, and in porting Python 2 wire format code. You may give some examples here: HTTP (Latin1 headers, binary body), SMTP, FTP, etc. > All the numeric formatting codes (such as ``%x``, ``%o``, ``%e``, ``%f``, > ``%g``, etc.) will be supported, and will work as they do for str, including > the padding, justification and other related modifiers. IMO you should give the exhaustive list here and we should only support one formatter for integers: %d. Python 2 supports "%d", "%u" and "%i" with "%u" marked as obsolete. Python 3.5 should not reintroduce obsolete formatters. If you want to use the same code base for Python 2.6, 2.7 and 3.5: modify your code to only use %d. Same rule apply for 2to3 tool: modify your source code to be compatible with Python 3. Please also mention all flags: #, +, -, '0', ' '. > ``%c`` will insert a single byte, either from an ``int`` in range(256), or > from > a ``bytes`` argument of length 1, not from a ``str``. I'm not sure that supporting bytes argument of 1 byte is useful, but it should not be hard to implement and may be convinient. > ``%s`` is restricted in what it will accept:: > > - input type supports ``Py_buffer`` [6]_? > use it to collect the necessary bytes > > - input type is something else? > use its ``__bytes__`` method [7]_ ; if there isn't one, raise a > ``TypeError`` Hum, you may mention that bytes(n: int) creates a bytes string of n null bytes, but b'%s' % 123 will raise an error because int.__bytes__() is not defined. Just to be more explicit. > ``%a`` will call :func:``ascii()`` on the interpolated value's > :func:``repr()``. > This is intended as a debugging aid, rather than something that should be > used > in production. Non-ascii values will be encoded to either ``\xnn`` or > ``\unnnn`` > representation. (You forgot "/Uhhhhhhhh" representation (it's an antislah, but I don't see the key on my Mac keyboard?).) What is the use case of this *new* formatter? How do you use it? print(b'%a" % 123) may emit a BytesWarning and may lead to bugs. IMO %a should be restricted for str%args. > It has been suggested to use ``%b`` for bytes as well as ``%s``. PyArg_ParseTuple() uses %y format for the exact bytes type. > > - Pro: clearly says 'this is bytes'; should be used for new code. > > - Con: does not exist in Python 2.x, so we would have two ways of doing > the > same thing, ``%s`` and ``%b``, with no difference between them. IMO it's useless, b'%s' % bytes just work fine in Python 2 and Python 3. -- I would like to help you to implement the PEP. IMO we should share as much code as possible with PyUnicodeObject. Something using the stringlib and maybe a new PyBytesWriter API which would have an API close to PyUnicodeWriter API. We should also try to share code between PyBytes_Format() and PyBytes_FromFormat(). Victor _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
