Documentation

The original documentionhttps://docs.python.org/3/library/shutil.html#shutil-platform-dependent-efficient-copy-operations about Platform-dependent efficient for Windows only mentioned thatshutil.copyfile(), but which is a bad read and write loop still.

Actually theshutil.copy2() used the Windows API COPYFILE2, which is faster, and native call which means don't copy to memory on userspace, and support copy-on-write.
So this should be mentioned in documention to let people know rather than only knowing until read all the opened issues on github and source code ofshutil.

Related info:
howshutil was implemented:#7160.
why onlyshutil.copy2() use Windows APICOPYFILE2 whileshutil.copyfile() not:#137074.
data that showsshutil.copy2() or Windows APICOPYFILE2 can accelerate transfer speed:https://github.com/antirotor/speedcopy.
PR of new version copy2 implemented:#105055.

Linked PRs

• gh-142407: Update shutil.rst to clarify copy performance on Windows #142408
• GH-142407: Doc: Clarify shutil.copyfile() does not use CopyFile2 on Windows #144354