The str->Unicode change widened IDLE/batch discrepancy. In python 2.x, bytes are printable. >>> for i in range(256): print i, chr(i) works fine. In python 3, chr has become (the old) unichr, and whether a unicode character is printable depends on the environment. In particular, under my Windows XP, the equivalent >>> for i in range(256): print (i, chr(i)) will still work fine under IDLE, but will now crash with an UnicodeEncodeError when run from the command line. ---------------- Unfortunately, I'm not sure what the right solution actually is, other than a mention in the Whats New document. I believe the 2.5 code was using a system page to print those characters, as they often looked like letters rather than <control>. Copying that would probably be the wrong solution. Limiting IDLE would add consistency, but might be a lot of work for the equivalent of a --pedantic flag. PEP 3138 seems to be proposing a default stdout BackslashReplace, which may at least help.

Whether or not that works in 3k depends on your console's encoding; your program works just fine for me in Linux, with a UTF-8 console. Python 2.5 was not using a "system page" (whatever that is); it was sending the bytes to the terminal as-is, which then could interpret them according to whatever encoding it choses to. Again, on a UTF-8 terminal, sending individual bytes above 128 is meaningless, so the console had to deal with it somehow. I fail to see a Python problem in this report, so I'm closing it as "works for me".