This is in the math module already, along with NaN:
In : import math
In : math.inf
In : math.nan
The same value
In : math.inf == float('inf')
but not the same object -- i.e. it's not a singleton.
In : math.inf is float('inf')
On Fri, Sep 4, 2020 at 9:49 AM Cade Brown firstname.lastname@example.org 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
- 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
*Cade Brown* Research Assistant @ ICL (Innovative Computing Laboratory) Personal Email: email@example.com ICL/College Email: firstname.lastname@example.org
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