Python bytecode STORE_NAME

[schwarz at cs.au.dk]

As part of some research I am doing a Python Virtual Machine in Java,
and the exact semantics of the STORE_NAME bytecode is unclear to be,
so I was hoping somebody here could clarify it.
The STORE_NAME bytecode is supposed to set a value for a name in the
current scope. However, the following piece of code:

def hello(who):
    print "Hello", who
    return hello(who)
print "Say:"
hello("World")

Results in this bytecode for the top level:
1, LOAD_CONST, 1
4, MAKE_FUNCTION, 0
7, STORE_NAME, 0
10, LOAD_CONST, 2
13, PRINT_ITEM, None
14, PRINT_NEWLINE, None
15, LOAD_NAME, 0
18, LOAD_CONST, 3
21, CALL_FUNCTION, 1
24, POP_TOP, None
25, LOAD_CONST, 0
28, RETURN_VALUE, None

And this bytecode for the hello function:
1, LOAD_CONST, 1
4, PRINT_ITEM, None
5, LOAD_FAST, 0
8, PRINT_ITEM, None
9, PRINT_NEWLINE, None
10, LOAD_GLOBAL, 1
13, LOAD_FAST, 0
16, CALL_FUNCTION, 1
19, RETURN_VALUE, None
20, LOAD_CONST, 0
23, RETURN_VALUE, None

The first column are the byte numbers, and the last column contains
the arguments to the byte codes if they take any.

The function is stored using STORE_NAME with offset 0 in the module
scope, but it is loaded from inside the hello method using LOAD_GLOBAL
with offset 1. My questions are: Does STORE_NAME add things to the
global scope when used top level? And why is the offset different?

The documentation contains nothing usable:
http://www.python.org/doc/2.5.2/lib/bytecodes.html

regards,
Mathias