Function to determine if two numbers are nearly equal when rounded to n significant decimal digits

Question

I have been asked to test a library provided by a 3rd party. The library is known to be accurate to n significant figures. Any less-significant errors can safely be

Answer 1

As of Python 3.5, the standard way to do this (using the standard library) is with the math.isclose function.

It has the following signature:

isclose(a, b, rel_tol=1e-9, abs_tol=0.0)

An example of usage with absolute error tolerance:

from math import isclose
a = 1.0
b = 1.00000001
assert isclose(a, b, abs_tol=1e-8)

If you want it with precision of n significant digits, simply replace the last line with:

assert isclose(a, b, abs_tol=10**-n)