Also, we should document the meaning of the other fields.  Several of them are not self explanatory:

min_10_exp = -307

   does not mean that 2.3e-308 isn't normalized

   does mean that 10**-307 is normalized and 10**-308 isn't


min_exp = -1021

   does not mean that 2**-1021 is the lowest normalized value

   does mean ldexp(0.5, -1021) == float_info.min


decimal_dig = 15

   does not mean digits required to specify every unique float

   does mean, "number of decimal digits, q, such that any 
   floating-point number with q decimal digits can be rounded
   into a floating-point number with p radix b digits and back
   again without change to the q decimal digits"