[Dan Christensen] > My student and I are writing a C extension that produces a large > integer in binary which we'd like to convert to a python long. The > number of bits can be a lot more than 32 or even 64. My student found > the function _PyLong_FromByteArray in longobject.h which is exactly > what we need, but the leading underscore makes me wary. Is it safe to > use this function?
Python uses it internally, so it better be ;-) > Will it continue to exist in future versions of python? No guarantees, and that's why it has a leading underscore: it's not an officially supported, externally documented, part of the advertised Python/C API. It so happens that I added that function, because Python needed some form of its functionality internally across different C modules. Making it an official part of the Python/C API would have been a lot more work (which I didn't have time for), and created an eternal new maintenance burden (which I'm not keen on regardless ;-)). In practice, few people touch this part of Python's implementation, so I don't /expect/ it will go away, or even change, for years to come. The biggest insecurity I can think of offhand is that someone may launch a crusade to make some other byte-array <-> long interface "official" based on a different way of representing negative integers. But even then I expect the current unofficial functions to remain, since the 256's-complement representation remains necessary for the `struct` module's "q" format, and for the `pickle` module's protocol=2 long serialization format. > Or is there some other method we should use? No. That's why these functions were invented to begin with ;-) -- http://mail.python.org/mailman/listinfo/python-list
