Gabriel Genellina wrote:
>>>> L = list(n for n in [globals(),locals()])
>>>> L[0] is L[1]
> True
>>>> L = list(n() for n in [globals,locals])
>>>> L[0] is L[1]
> False
>
> (I think this has to do with free variables in the "right side" (after
> the "in" keyword) of a generator expression; they appear to be evaluated
> when the expression is *defined*, not when is is *used*. By contrast, free
> variables in the "left side" appear to be evaluated when the expression is
> used.)
Indeed, the right side is evaluated in the enclosing namespace and then
passed as an argument to the genexpr:
>>> dis.dis(compile("(x for y in z)", "nofile", "exec"))
1 0 LOAD_CONST 0 (<code object <genexpr> at
0x2b22b2dcf828, file "nofile", line 1>)
3 MAKE_FUNCTION 0
6 LOAD_NAME 0 (z)
9 GET_ITER
10 CALL_FUNCTION 1
13 POP_TOP
14 LOAD_CONST 1 (None)
17 RETURN_VALUE
Peter
--
http://mail.python.org/mailman/listinfo/python-list
