Underscores in Python numbers

[Roy Smith]

cookedm+news at physics.mcmaster.ca (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.

You have described, if memory serves, a Taylor series, and those 
coefficients are 1/3!, 1/5!, 1/7!, etc.  What I would do, rather than 
embedding the numeric constants in the code, is embed the formula and have 
the machine compute the actual values at import time.  At the very least, 
have them machine generated and saved.  You certainly don't want to be 
typing in long strings of digits like that.