Given that this is unlikely to see any change in core Python, perhaps you can get a decent solution with a third party library? If your main issue is that repr doesn't provide an "eval-able" string, then may I suggest using the "most-used" function in the ubelt utility library: ubelt.repr2

Two main goals of repr2 are to provide nice string representations of nested
data structures and make those "eval-able" whenever possible. As an example
take the value `float('inf')`, which normaly has a non-evalable repr of `inf`:

>>> !pip install ubelt
>>> import ubelt as ub
>>> ub.repr2(float('inf'))
"float('inf')"

The `newline` (or `nl`) keyword argument can control how deep in the nesting
newlines are allowed.

>>> print(ub.repr2({1: float('nan'), 2: float('inf'), 3: 3.0}))
{
1: float('nan'),
2: float('inf'),
3: 3.0,
}

>>> print(ub.repr2({1: float('nan'), 2: float('inf'), 3: 3.0}, nl=0))
{1: float('nan'), 2: float('inf'), 3: 3.0}

You can also define or overwrite how representations for different types are
created. You can either create your own extension object, or you can
monkey-patch `ub.util_format._FORMATTER_EXTENSIONS` without specifying the
extensions keyword argument (although this will be a global change).

>>> extensions = ub.FormatterExtensions()
>>> @extensions.register(float)
>>> def my_float_formater(data, **kw):
>>> return "monkey({})".format(data)
>>> print(ub.repr2({1: float('nan'), 2: float('inf'), 3: 3.0}, nl=0, extensions=extensions))
{1: monkey(nan), 2: monkey(inf), 3: monkey(3.0)}

On Fri, Sep 4, 2020 at 12:49 PM Cade Brown <brown.cade@gmail.com> wrote:

I am positing that Python should contain a constant (similar to True, False, None), called Infinity.

It would be equivalent to `float('inf')`, i.e. a floating point value representing a non-fininte value. It would be the positive constant; negative infinity could retrieved via `-Infinity`

Or, to keep float representation the same, the name `inf` could be used, but that does not fit Python's normal choice for such identifiers (but indeed, this is what C uses which is the desired behavior of string conversion)

I think there are a number of good reasons for this constant. For example:
* It is also a fundamental constant (similar to True, False, and None), and should be representable as such in the language
* Requiring a cast from float to string is messy, and also obviously less efficient (but this performance difference is likely insignificant)
* Further, having a function call for something that should be a constant is a code-smell; in general str -> float conversion may throw an error or anything else and I'd rather not worry about that.
* It would make the useful property that `eval(repr(x)) == x` for floating point numbers (currently, `NameError: name 'inf' is not defined`)

This makes it difficult to, for example, naively serialize a list of floats. For example:

```
>>> x = [1, 2, 3, 4]
>>> repr(x)
'[1, 2, 3, 4]'
>>> eval(repr(x)) == x
True
>>> x = [1, 2, 3, float('inf')]
>>> repr(x)
'[1, 2, 3, inf]'
>>> eval(repr(x)) == x
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<string>", line 1, in <module>
NameError: name 'inf' is not defined
```

To me, this is problematic; I would expect it to work seamlessly as it does with other floating point constants.

A few rebuttals/claims against:
- Creating a new constant (Infinity) which is unassignable may break existing code
- Converting a float to string is not the same as it is in C. Whil

I also realize that there is `math.inf`, but I argue that the constant is more fundamental than that, and it still doesn't solve the problem with `repr()` I described

Thanks,
----
Cade Brown
Research Assistant @ ICL (Innovative Computing Laboratory)
Personal Email: brown.cade@gmail.com
ICL/College Email: cade@utk.edu

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