> Indeed, fwrite() can return expected number of items and set errno. Here is a simple example on C. An output is:

Yeah, who's volunteering to report it to the glibc?

That's not a python bug, but I feel bad ignoring it.

Note that ferror() isn't reliable (not on my box at least), so we have to use errno directly.
And of course keep the check that the value returned by fwrite matches.