[Python-Dev] Fast access to __builtins__
Thu, 27 Mar 2003 23:24:50 +0100
Raymond Hettinger wrote:
>>From past rumblings, I gather that Python is moving
> towards preventing __builtins__ from being shadowed.
> I would like to know what you guys think about going ahead
> with that idea whenever the -O optimization flag is set.
> The idea is to scan the code for lines like:
> LOAD_GLOBAL 2 (range)
> and, if the name is found in __builtins__, then lookup
> the name, add the reference to the constants table and,
> replace the code with something like:
> LOAD_CONST 5 (<type 'range'>)
Using the -O for this is not a working possibility. -OO
is reserved for optimizations which can change semantics,
but even there, I'd rather like a per-module switch than
a command line switch.
BTW, why not have a new opcode for symbols in the
builtins and then only tweak the opcode implementation
instead of having the compiler generate different code ?
> The opcode replacement bypasses module level shadowing
> but leaves local shadowing intact. For example:
> modglob = 1
> range = xrange
> def f(list):
> for i in list: # local shadowing of 'list' is unaffected
> print ord(i) # access to 'ord' is optimized
> j = modglob # non-shadowed globals are unaffected
> k = range(j) # shadowing of globals is ignored
> I've already tried out a pure python proof-of-concept and it is
> straightforward to recode it in C and attach it to PyCode_New().
> Raymond Hettinger
> Python-Dev mailing list
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