[Python-Dev] Allocation of shape and strides fields in Py_buffer (original) (raw)

Greg Ewing greg.ewing at canterbury.ac.nz
Thu Dec 11 01:21:56 CET 2008

Antoine Pitrou wrote:

- it uses something (Pybuffer) which is not a PyObject and has totally different allocation/lifetime semantics

This was a deliberate decision -- in fact I argued for it myself. The buffer interface is meant to be a minimal-overhead way for C code to get at the underlying data. Requiring allocation of a PyObject would be too expensive.

The way to think about the Py_buffer struct is not as an object in its own right, but just a place to put some output parameters from the GetBuffer call.

The lifetime of the information pointed to by the Py_buffer is the same as the lifetime of the underlying object, and that object is responsible for managing it.

- it doesn't specify how to obtain e.g. a sub-buffer, or even duplicate an existing one (which seem to be rather fundamental actions to me)

I don't think they're as fundamental as all that. But some utilities for doing things like this could be useful, as I mentioned in another post.

-- Greg

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