On Sun, Mar 15, 2020 at 6:12 PM Stephen J. Turnbull <
turnbull.stephen...@u.tsukuba.ac.jp> wrote:
> Also, I'd like to note that "inf" and "-inf" (and "nan" for that
> matter) are not "informal". They are readable input, part of Python
> syntax:
>
> % python3.8
> Python 3.8.2 (default, Feb 27 2020, 19:58:50)
> >>> float("inf")
> inf
> >>> float("-inf")
> -inf
>
which, of course is what __repr__ is supposed to do, though in this case it
doesn't quite:
In [11]: fp = float("inf")
In [12]: eval(repr(fp))
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
<ipython-input-12-4f5249ac51be> in <module>
----> 1 eval(repr(fp))
<string> in <module>
NameError: name 'inf' is not defined
So they are not "readable input, part of Python syntax", but they are part
of the float API.
Anyway, Python now has two different ways to "turn this into a string":,
__str__ and __repr__. I think the OP is suggesting a third, for "pretty
version". But then maybe folks would want a fourth or fifth, or .....
maybe we should, instead, think about updating the __str__ for standard
types.
Is there any guarantee (or even string expectation) that the __str__ for an
object won't change?
I've always wondered why the standard str(some object) wasn't pretty to
begin with.
As for using unicode symbols for things like float("inf") -- that would be
an inappropriate for the __repr__, but why not __str__ ?
*reality check*: I imagine a LOT of code out there (doctests, who know what
else) does in fact expect the str() of builtins not to change -- so this is
probably dead in the water.
-CHB
--
Christopher Barker, PhD
Python Language Consulting
- Teaching
- Scientific Software Development
- Desktop GUI and Web Development
- wxPython, numpy, scipy, Cython
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