On Feb 13, 10:19 pm, Tobiah <[EMAIL PROTECTED]> wrote:
> >>> print float(3.0) is float(3.0)
> True
> >>> print float(3.0 * 1.0) is float(3.0)
> False
[You don't need to wrap your floats in float()]
>>> def f():
... return 3.0 is 3.0, 3.0*1.0 is 3.0
...
>>> f()
(True, False)
>>> import dis
>>> dis.dis(f)
2 0 LOAD_CONST 1 (3.0)
3 LOAD_CONST 1 (3.0)
6 COMPARE_OP 8 (is)
9 LOAD_CONST 3 (3.0)
12 LOAD_CONST 1 (3.0)
15 COMPARE_OP 8 (is)
18 BUILD_TUPLE 2
21 RETURN_VALUE
As you can see when "3.0 is 3.0" is evaluated the same float object is
put on the stack twice so the 'is' comparison is True (LOAD_CONST 1 /
LOAD_CONST 1 / COMPARE_OP 8).
Whereas when "3.0*1.0 is 3.0" is evaluated, *two* different float
objects are put on the stack and compared (LOAD_CONST 3 / LOAD_CONST
1 / COMPARE_OP 8). Therefore the result is False.
HTH
--
Arnaud
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