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? Especially as it does constant folding if the order is
reversed:
>>> def f(x):
... return 1024 * 1024 * x
...
>>> dis(f)
2 0 LOAD_CONST 2 (1048576)
3 LOAD_FAST 0 (x)
6 BINARY_MULTIPLY
7 RETURN_VALUE
I'm cool with defining things as a constant and using those instead
or front-loading my constants in my expressions, but the disparity
struck me as a little odd. Any insights on the reasons/motivations
for one and not the other?
-tkc
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