Re: [matplotlib-devel] Experiments in removing/replacing PyCXX

[Chris B. - N. F. <chr...@no...>]

On Mon, Dec 3, 2012 at 4:16 PM, Nathaniel Smith <nj...@po...> wrote:

> Yeah, this is a general problem with the Python file API, trying to
> hook it up to stdio is not at all an easy thing. A better version of
> this code would skip that altogether like:
>
> cdef void write_to_pyfile(png_structp s, png_bytep data, png_size_t count):
>     fobj = <object>png_get_io_ptr(s)
>     pydata = PyString_FromStringAndSize(data, count)
>     fobj.write(pydata)

Good point -- not at all Cython-specific, but do you need libpng (or
whatever) to write to the file? can you just get a buffer with the
encoded data and write it on the Python side? Particularly if the user
wants to pass in an open file object. This might be a better API for
folks that might want stream an image right through a web app, too.

As a lot of Python APIs take either a file name or a file-like object,
perhaps it would make sense to push that distinction down to the
Cython level:
  -- if it's a filename, open it with raw C
  -- if it's a file-like object, have libpng write to a buffer (bytes
object) , and pass that to the file-like object in Python

anyway, not really a Cython issue, but that second object sure would
be easy on Cython....

-Chris


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Chr...@no...