Python 3 is not affected by this bug.

In Python 3, the full I/O stack was rewritten from scratchn, the new io module has a different design. Reading ahead still exists in the io module, but it is now done by a dedicated object: io.BufferedReader, and this object uses a lock to prevent concurrent reads. A single thread controls the file position at the same time. (Except if a different thread uses directly the file descriptor, but that's a different story.)