[Python-Dev] PEP 515: Underscores in Numeric Literals

[Georg Brandl]

On 02/11/2016 10:10 AM, Paul Moore wrote:
> On 10 February 2016 at 23:14, Steven D'Aprano <steve at pearwood.info> wrote:
>> On Wed, Feb 10, 2016 at 10:53:09PM +0000, Paul Moore wrote:
>>> On 10 February 2016 at 22:20, Georg Brandl <g.brandl at gmx.net> wrote:
>>> > This came up in python-ideas, and has met mostly positive comments,
>>> > although the exact syntax rules are up for discussion.
>>>
>>> +1 on the PEP. Is there any value in allowing underscores in strings
>>> passed to the Decimal constructor as well? The same sorts of
>>> justifications would seem to apply. It's perfectly arguable that the
>>> change for Decimal would be so rarely used as to not be worth it,
>>> though, so I don't mind either way in practice.
>>
>> Let's delay making any change to string conversions for now, and that
>> includes Decimal. We can also do this:
>>
>> Decimal("123_456_789.00000_12345_67890".replace("_", ""))
>>
>> for those who absolutely must include underscores in their numeric
>> strings. The big win is for numeric literals, not numeric string
>> conversions.
> 
> Good point. Maybe add this as an example in the PEP to explain why
> conversions are excluded. But I did only mean the Decimal constructor,
> which I think of more as a "decimal literal" - whereas int() and
> float() are (in my mind at least) conversion functions and as such
> should not be coupled to literal format (for example, 0x0001 notation
> isn't supported by int())

Actually, it is.  Just not without a base argument, because the default
base is 10.  But both with base 0 and base 16, '0x' prefixes are allowed.

That's why I'm leaning towards supporting the underscores.  In any case
I'm preparing the implementation.

Georg