On Fri, Aug 1, 2014 at 7:29 AM, Emile van Sebille <em...@fenx.com> wrote:
> And which is also how it works:
>
> Python 2.5 (r25:51908, Dec 18 2009, 14:22:21)
> [GCC 3.4.6 20060404 (Red Hat 3.4.6-3)] on linux2
> Type "help", "copyright", "credits" or "license" for more information.
>>>>
>>>> def test():p = {'k':"value0",'k':"value1"}
> ...
>>>> from dis import dis
>>>> dis(test)
> 1 0 BUILD_MAP 0
> 3 DUP_TOP
> 4 LOAD_CONST 1 ('value0')
> 7 ROT_TWO
> 8 LOAD_CONST 2 ('k')
> 11 STORE_SUBSCR
> 12 DUP_TOP
> 13 LOAD_CONST 3 ('value1')
> 16 ROT_TWO
> 17 LOAD_CONST 2 ('k')
> 20 STORE_SUBSCR
> 21 STORE_FAST 0 (p)
> 24 LOAD_CONST 0 (None)
> 27 RETURN_VALUE
Python 2.5 is quite old now, but here's the 2.7 disassembly for the same code:
>>> dis.dis(test)
1 0 BUILD_MAP 2
3 LOAD_CONST 1 ('value0')
6 LOAD_CONST 2 ('k')
9 STORE_MAP
10 LOAD_CONST 3 ('value1')
13 LOAD_CONST 2 ('k')
16 STORE_MAP
17 STORE_FAST 0 (p)
20 LOAD_CONST 0 (None)
23 RETURN_VALUE
I believe it's still doing the same thing. My reading of this is:
"Create a map with room for two elements. Stick this value on the
stack, stick this key on the stack, stow it in the map. Repeat last
sentence with a different value. Now store that resulting map." So
it's still just happily overriding, although the code is different
from the assignment version:
>>> dis.dis(test2)
1 0 BUILD_MAP 0
3 STORE_FAST 0 (p)
6 LOAD_CONST 1 ('value0')
9 LOAD_FAST 0 (p)
12 LOAD_CONST 2 ('k')
15 STORE_SUBSCR
16 LOAD_CONST 3 ('value1')
19 LOAD_FAST 0 (p)
22 LOAD_CONST 2 ('k')
25 STORE_SUBSCR
26 LOAD_CONST 0 (None)
29 RETURN_VALUE
ChrisA
--
https://mail.python.org/mailman/listinfo/python-list
