[lntue]

I don't know much about numpy.signal package, but there are other python packages that have good implementation for generating polynomial approximation. Among them are pythonsollya (a Python wrapper for Sollya), and SageMath.

Other than that, some of the overview references about Remez algorithm (should be a bit closer to your taste) that I like are:

- J.M. Muller et. al., "Handbook of Floating-Point Arithmetic", section 10.3.2 (and follow references in that section).

- N. Brisebarre and S. Chevillard, "Efficient polynomial L-approximations," 18th IEEE Symposium on Computer Arithmetic (ARITH '07), which is implemented in Sollya tool: https://www.sollya.org/sollya-2.0/help.php?name=fpminimax