[Python-ideas] 'Infinity' constant in Python

4 Sep 2020

      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