To be more specific for those wanting to follow your advice, use nextafter to compute +Eps, +1+Eps, etc. rather than assume it's a fixed value like DBL_EPSILON.

To be more specific for those wanting to follow your advice, use nextafter to compute +Eps, +1+Eps, etc. rather than assume it's a fixed value like DBL_EPSILON. >>> from math import nextafter >>> nextafter(0, 1) 5e-324 >>> nextafter(0, -1) -5e-324 >>> nextafter(-1, -10) -1.0000000000000002 My numeric code became much more robust once I started doing this, including using it to find test cases, for example, by computing all distinct rationals (up to a given denominator) in my range of interest, then using nextafter() to generate all values within 5 or so steps from that rational. For example, one algorithm I had failed with values like 0.21000000000000002 and 0.39999999999999997 , which are one step away from 0.21 and 0.4, respectively.