Python arithmetic with small numbers

Question

I am getting the following unexpected result when I do arithmetic with small numbers in Python:

>>> sys.float_info
sys.float_info(max=1.797693134862         


        

Answer 1

it should be able to handle "large" small numbers like 1e-17, shouldn't it?

Not necessarily (it depends on the numbers). A float cannot exactly represent either 1e-17 or 1-(1e-17). In the case of the latter, the nearest number that it can represent is 1.

I suggest you read What Every Computer Scientist Should Know About Floating-Point Arithmetic.