With 3.4.3 from an OS X terminal prompt, if I just enter the interactive Python REPL environment (by just entering the command "python" from the command line) and then exit (via "exit()" or Ctrl-D), then stdout appears to be broken ... I see no stdout output on the terminal from that point forward. I do see stderr output.

If I just run a python script, without the "-i" flag, then stdout is not damaged and the subsequent terminal interaction is normal.

I did not see this with 3.4.2 or any other version of Python.

I'm running OS X 10.9.5, have installed Python 3.4.3 with MacPorts, and use virtualenv.

There have been other problems reported with MacPorts Python 3.4 using their default most recent version of the BSD libedit package.  As far as I know, those problems have not yet been resolved but I can't get to the MacPorts issue tracker at the moment to check.  The workaround has been to install the optional py34-readline port which modifies the MacPorts python3.4 to use GNU readline rather than libedit.  In any case, you can follow up on the MacPorts tracker (https://trac.macports.org) as this is not a problem seen with a vanilla Python 3.4.x on OS X using the Apple-supplied system version of libedit.

Thanks. I installed py34-readline and rebuilt my virtualenv; all is well now.

I put in a MacPorts ticket when their bugtracker gets back online.