Does Python support zero-copy I/O?

Question

I have two open file objects, dest and src. File object dest is opened for writing, with the seek position placed at some offset within th

Answer 1

Since version 3.3, Python has os.sendfile, which interfaces to various Unix variants' sendfile(2) zero-copy I/O interfaces. It operates on file descriptors, not general file-like objects. For older Pythons, there's py-sendfile.

Answer 2

Since Python 3.8, you can use shutil.copyfile (and others from shutil) which will internally use zero-copy if possible, such as os.sendfile, and if not possible, fall back to a simple read-write loop.

See the shutil docs for details. Or issue 33671 (Efficient zero-copy for shutil.copy* functions (Linux, OSX and Win)). And the corresponding (merged) pull request.

You might also be interested in copy-on-write support or server-side copy support. See here, here. The os.copy_file_range (since Python 3.8) would do that. See issue 37159 (Use copy_file_range() in shutil.copyfile()) (maybe Python 3.9 or 3.10).