Josiah Carlson wrote:
Ron Adam <rrr@ronadam.com> wrote:
Interpretation:
The "small" inconsistency (if any) here is the 'not' keyword vs the 'bool()' constructor. They pretty much do the same thing yet work in modestly different ways.
Maybe I'm missing something, but is there a place where the following is true?
(not not x) != bool(x)
I can't think of any that I've ever come across.
- Josiah
I don't think you are missing anything. I did say it was a *small* inconsistency in how they are used in relation to 'and', 'or' and 'not'. ie.. a constructor vs a keyword in a similar situation. And I also pointed out it doesn't change what they do, it has more to do with how they work underneath and that there may be some benefits in changing this.
def foo(x): ... return (not not x) != bool(x) ... dis.dis(foo) 2 0 LOAD_FAST 0 (x) 3 UNARY_NOT 4 UNARY_NOT 5 LOAD_GLOBAL 0 (bool) 8 LOAD_FAST 0 (x) 11 CALL_FUNCTION 1 14 COMPARE_OP 3 (!=) 17 RETURN_VALUE
In this case the lines... 5 LOAD_GLOBAL 0 (bool) 8 LOAD_FAST 0 (n) 11 CALL_FUNCTION 1 Would be replaced by... 5 LOAD_FAST 0 (n) 6 UNARY_BOOL The compiler could also replace UNARY_NOT, UNARY_NOT pairs with a single UNARY_BOOL. There may be other situations where this could result in different more efficient byte code as well. _Ron