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
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