Compile time evaluation of dictionaries

[Jean-Michel Pichavant]

Gerald Britton wrote:
> Today I noticed that an expression like this:
>
> "one:%(one)s two:%(two)s" % {"one": "is the loneliest number", "two":
> "can be as bad as one"}
>
> could be evaluated at compile time, but is not:
>
>   
>>>> dis(compile(
>>>>         
> ... '"one:%(one)s two:%(two)s" % {"one": "is the loneliest number",
> "two": "can be as bad as one"}',
> ... '','exec'))
>  1           0 LOAD_CONST               0 ('one:%(one)s two:%(two)s')
>              3 BUILD_MAP                2
>              6 LOAD_CONST               1 ('is the loneliest number')
>              9 LOAD_CONST               2 ('one')
>             12 STORE_MAP
>             13 LOAD_CONST               3 ('can be as bad as one')
>             16 LOAD_CONST               4 ('two')
>             19 STORE_MAP
>             20 BINARY_MODULO
>             21 POP_TOP
>             22 LOAD_CONST               5 (None)
>             25 RETURN_VALUE
>   
>
> Any idea why Python works this way?  I see that, in 3.2, an
> optimization was done for sets (See "Optimizations" at
> http://docs.python.org/py3k/whatsnew/3.2.html) though I do not see
> anything similar for dictionaries.
>
> --
> Gerald Britton
>
>
>
>   
1/ because no one would ever see the difference.
2/ immutables can always be evaluated before any high CPU consuming loop
3/ it would make the implementation more complex (i.e. more work for our 
beloved active community) for no gain
4/ you can write C code to speed up things: 
http://docs.python.org/extending/extending.html, when really needed.

JM