[Python-ideas] Default return values to int and float

[MRAB]

On 05/10/2011 19:33, Ron Adam wrote:
> On Wed, 2011-10-05 at 08:06 -0700, Ethan Furman wrote:
>> Ron Adam wrote:
>>> I really don't like the '-1' for a not found case. They just get in the
>>> way.
>>>
>>> If len(s) was the not found case, you get a value that can be used in a
>>> slice without first checking the index, or catching an exception.
>>
>> So every time we want to know if s.find() failed, we have to compare to
>> len(s)?
>
> I think probably None would have been better than -1. At least then you
> will get an error if you try to use it as an index.
>
None will be rejected as an index, but not as part of a slice:

 >>> s = "abcdef"
 >>> s[None : 4]
'abcd'
 >>> s[4 : None]
'ef'

> The problem with len(s) as a failure, is when you consider rfind(). It
> should return 1 before the beginning, which coincidentally it does, but
> you still can't use it as a slice index because it will give you 1 from
> the end instead.
>
> So until we find a another way to do negative sequence indexing. It
> won't quite work as nice as it should.
>