Re: [Python-ideas] `numbers.Natural`

26 Sep 2014


      On 09/26/2014 02:04 PM, David Mertz wrote:
...
On Fri, Sep 26, 2014 at 1:57 PM, Thomas Gläßle mailto:t_glaessle@gmx.de> wrote
And more importantly: you wouldn't expect isNatural(3.5) to return True.
That's not a problem with my one-liner, nor Ian's:
...
...
...
isNatural = lambda x: int(x)==x and x>0
isNatural(3.5)
False
However, my correction to avoid crashing on some inputs is still wrong, given:
...
...
...
isinstance(0j, numbers.Number)
True
int(0j)
TypeError
So I think I really need a couple lines:
def isNatural(x):
         try:
             return int(x)==x and x>0
         except (TypeError, ValueError):
             return False
If we had PEP 463 [1] it could still be a one-liner ;)

   def is_natural(x):
       return int(x) == x and x > 0 except TypeError, ValueError: False

--
~Ethan~


[1] http://legacy.python.org/dev/peps/pep-0463/

Re: [Python-ideas] `numbers.Natural`

Ethan Furman