[Python-3000] Reconsider repr(0.1) == '0.10000000000000001'

[Noam Raphael]

Hello,

I would like to re-raise the issue of float repr() -- making repr(1.1)
== '1.1' instead of '1.1000000000000001'.

My use case is data manipulation in the interactive shell - an
extremely powerful tool which, it seems, not so many people use. Many
times I have float data. I think that you'll agree with me that, for
example:

>>> height['Alice']
1.67

Is much easier to understand than

>>> height['Alice']
1.6699999999999999

Not to mention

>>> height
{'David': 1.81, 'Alice': 1.67, 'Bob': 1.76, 'Barbara': 1.65}

Versus:

>>> height
{'Bob': 1.76, 'Barbara': 1.6499999999999999, 'Alice':
1.6699999999999999, 'David': 1.8100000000000001}


I think that the reason for the long representation is that it uses a
simple algorithm that makes "eval(repr(f)) == f" always true. However,
why not use another, a bit more complex, algorithm, which will still
preserve "eval(repr(f)) == f", but which will shorten the result when
it can?

You see, it's not even that the current algorithm is exact - for
example, the actual, stored, representation of 1.67 is, on my
computer, 1.1010101110000101000111101011100001010001111010111. The
exact decimal representation of that number is
1.6699999999999999289457264239899814128875732421875. I agree that
"1.6699999999999999" is better, but isn't "1.67" the best?

Have a good day,
Noam