STINNER Victor <vstinner@python.org> added the comment: TextIOWrapper, and maybe also BufferedRead, may raise an exception if the underlying file descriptor is configured in non-blocking mode. It may require an additional syscall() to query the FD properties, which may slowdown the creation of file objects in Python :-/ ---------- _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue13322> _______________________________________