I have a source code which IDLE 3.0a5 cannot parse, but Python 3.0a5 
can (also attached): 

#!/usr/bin/python
# -*- coding: utf-8 -*-

def načtiSlovník(zdroj='slovník.txt'):
    soubor = open(zdroj, mode='r', encoding='utf_8')
    řádky = soubor.readlines()
    for řádek in řádky:
        print(řádek, end='')

načtiSlovník()
# End of source code


I have set up Default Source Encoding to UTF-8 in IDLE's general 
configuration. Still, when I open that source code and try to run it, 
IDLE complains about "invalid character in identifier" and highlights 
"zdroj" red in the first line (sic!). 

However, when I run the source code from command line (by "python 
<filename>"), it gets executed well and does what it shall do. 

I should probably add, that I have installed py3k:62932M, May 9 2008, 
16:23:11 [MSC v.1500 32 bit (Intel)] on win32. I use Windows XP SP 3. 
IDLE uses Tk version 8.4