Underscores in Python numbers

[D H]

Steve Holden wrote:
> David M. Cooke wrote:
>> One example I can think of is a large number of float constants used
>> for some math routine. In that case they usually be a full 16 or 17
>> digits. It'd be handy in that case to split into smaller groups to
>> make it easier to match with tables where these constants may come
>> from. Ex:
>>
>> def sinxx(x):
>>     "computes sin x/x for 0 <= x <= pi/2 to 2e-9"
>>     a2 = -0.16666 66664
>>     a4 =  0.00833 33315
>>     a6 = -0.00019 84090
>>     a8 =  0.00000 27526
>>     a10= -0.00000 00239
>>     x2 = x**2
>>     return 1. + x2*(a2 + x2*(a4 + x2*(a6 + x2*(a8 + x2*a10))))
>>
>> (or least that's what I like to write). Now, if I were going to higher
>> precision, I'd have more digits of course.
>>
> Right, this is clearly such a frequent use case it's worth changing the 
> compiler for.

Yes it is.
In that one example he used digit grouping 5 more times than I've
used lambda in my life.  Remember people use python as a data format as 
well (see for example JSON).
It's a simple harmless change to the parser: ignore underscores or 
spaces in numeric literals.  As others have mentioned, Ruby supports
this already, as do Ada, Perl, ML variants, VHDL, boo, nemerle, and others.