Python 3.1.2 hasn't any arguments except the file name in sys.argv[0]. For example: build.py test
sys.argv[1] will be empty. I tried even the first example from the documentation 15.4 (optparse) but the filename is None. In Python 2.6.5 all is working fine.

It's not entirely clear to me what issue you're reporting here:  could you provide a short example script that exhibits the problem, and list the exact steps necessary to reproduce, along with actual and expected results?

Examplescript test.py:

import sys
print(sys.argv[1])


Call this script now with an argument, for exmaple: test.py 1234
I expect to see the string 1234 in the console but Python 3 says "IndexError: list index out of range". With Python 2.6.5 I be able to see the correct string 1234.

Can’t reproduce here:
$ python3.1 -c "import sys; print(sys.argv[1])" 1234
1234
$ python3.1 --version
Python 3.1.2

Hmm.  I don't see any difference between the two here (OS X 10.6).  What platform are you on, and where did your copy of Python 3.1.2 come from?

newton:~ dickinsm$ cat test.py
import sys
print(sys.argv[1])
newton:~ dickinsm$ python3.1 test.py 1234
1234
newton:~ dickinsm$ python2.6 test.py 1234
1234
newton:~ dickinsm$ python3.1
Python 3.1.2 (r312:79147, May 18 2010, 17:21:15) 
[GCC 4.2.1 (Apple Inc. build 5659)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> 
newton:~ dickinsm$ python2.6
Python 2.6.5 (r265:79063, May 18 2010, 17:12:15) 
[GCC 4.2.1 (Apple Inc. build 5659)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>>

I'm using Windows XP Professional SP3. I downloaded Python 3.1.2 from this site. Even Python 3.0.1 hasn't worked.

3.0 should not be used and does not get fixes.

Can you try downloading Python again and testing?

P.S. please do not change the component; Lib means “Python files under Lib/ in the source checkout”, but sys is a module built by the interpreter core.

I have already installed Python 3.1.2 a second time. I have selected during the installation that the files shall be compiled into bytecode.

I'm failing to reproduce this on Windows 7, too.

It sounds as though you're starting the python script without an explict 'python'.  What are your filetype associations for python scripts?

i.e., what's the result of typing 'assoc py' at a console prompt?
And what's the result of the 'ftype' command for the above?

Just for reference, I get:

>assoc.py
.py=Python.File

>ftype Python.File
Python.File=C:\Python31\python.exe "%1" %*

assoc .py
.py=Python.File

I tried this now with Ubuntu and Python 3.1.2 and all works fine. But under Windows XP it doesn't work.

Okay, thanks.  What does

ftype Python.File

give?

ftype Python.File
Python.File="E:\Python31\python.exe" "%1" %*

I've just found issue #7936, which looks like the same problem.  I'm going to close this issue as a duplicate of that one;  further discussion should be moved there.