"Brian van den Broek" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> Is the right way to understand it in this vicinity:
In the vicinity, but not quite exact
>At compile time (by which I mean when the Python bytecode is built)
Compile time is when the def statement is executed
>the global statement is hit and has the effect of `bumping up' the
>function local name `x' to the module namespace, making the function local
>name `x' synonymous with the module global name `x'.
Global make 'x' global. Period. There is no local 'x'.
> At runtime, the `global x' is never reached,
In CPython, at least, it is not even there to be reached (see below).
It is strictly a compile time declaration. At runtime, it is equivalent to
'pass'.
> but it has already, at compile time, had its effect on the nature of the
> function object
Right. With 2.2:
def f():
if False: global x
x = 1
import dis
dis.dis(f)
0 SET_LINENO 1
3 SET_LINENO 2
6 LOAD_GLOBAL 0 (False)
9 JUMP_IF_FALSE 7 (to 19)
12 POP_TOP
13 SET_LINENO 2
16 JUMP_FORWARD 1 (to 20)
>> 19 POP_TOP
>> 20 SET_LINENO 3
23 LOAD_CONST 1 (1)
26 STORE_GLOBAL 1 (x)
29 LOAD_CONST 0 (None)
32 RETURN_VALUE
Two points: there is no byte code for the global declaration; x is directly
stored as global.
Terry J. Reedy
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