On Fri, Mar 24, 2017 at 1:35 PM, Tim Chase <python.l...@tim.thechases.com> wrote: > Playing around, I came across the following > > $ python3 > Python 3.4.2 (default, Oct 8 2014, 10:45:20) > [GCC 4.9.1] on linux > Type "help", "copyright", "credits" or "license" for more information. >>>> from dis import dis >>>> def f(x): > ... return x * 1024 * 1024 > ... >>>> dis(f) > 2 0 LOAD_FAST 0 (x) > 3 LOAD_CONST 1 (1024) > 6 BINARY_MULTIPLY > 7 LOAD_CONST 1 (1024) > 10 BINARY_MULTIPLY > 11 RETURN_VALUE > > Is there any reason that Python doesn't do the constant folding of > 1024 * 1024?
Because that expression is equivalent to (x * 1024) * 1024, not x * (1024 * 1024). If x is a built-in type like int or list then that may be equivalent to x * 1048576, but the compiler can't know that x is necessarily one of those things. -- https://mail.python.org/mailman/listinfo/python-list
