[C++-sig] boost::python::str and Python's str and unicode types

[Haoyu Bai]

On Tue, Jul 28, 2009 at 10:11 PM, Robert
Smallshire<Robert.Smallshire at roxar.com> wrote:
>
>> On 07/23/2009 10:17 AM, Robert Smallshire wrote:
>> > Hello,
>> >
>> > I'm looking for some confirmation that my understanding of what
>> > boost.python is doing is correct.
>> >
>> > > From what I understand boost::python::str represents the str
>> > (PyStringObject) type in Python.  Unless I'm missing
>> something, here
>> > doesn't seem to be anything like boost::python::unicode
>> representing
>> > the unicode type (PyUnicodeObject).
>> >
>> > Boost.Python does have a built-in conversion from std::wstring to
>> > object, but this creates a str in Python, so presumably
>> there is some
>> > (lossy?) decoding going on here.
>> >
>> > It seems that to directly create a PyUnicodeObject from C++ I will
>> > need to do one or more of the following:
>> >
>> > 1) Directly use the Python C API to create and manipulate
>> > PyUnicodeObject.
>> > 2) Create my own subclass of boost::python::object called
>> for example
>> > 'unicode', which would be similar to the str class provided
>> out of the
>> > box, but would use PyUnicodeObject underneath and deal with wchar_t
>> > rather than char.
>
> I have modified my local build of boost.python to include a
> boost::python::unicode class, together with appropriate conversions from
> wchar, const wchar_t* and std::wstring, together with additional tests
> in the boost.python test suite.  As you would expect, the code is
> closely derived from the existing boost::python::str code but uses the
> Python C API for PyUnicode_Type rather than PyString_Type. There are no
> breaking changes to the existing boost.python API.
>
> I'd like to contribute these changes back to boost.python so they can be
> hopefully integrated into future official Boost releases.  What is the
> procedure for this?  Where do I start?
>
> Cheers,
>
> Robert Smallshire
>
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Hi,

Sorry for the delayed reply because I was busy on some other stuff last week.

Currently the unicode support I implemented for Python 3 contains some
converters for PyUnicode and C++ string types, and a
boost::python::str class that conditionally call PyUnicode API in
Python 3 or PyString API in Python 2. So a boost::python::unicode type
would be very useful for Python 2. And for Python 3, we might need to
rename the new "unicode" class to "str", and the old "str" class to
"bytes", in order to reflect the change of Python.

I'd happy to help to integrate and test it if send your code to the boost trac.

Thank you!

-- 
Haoyu Bai
School of Computing,
National University of Singapore.