  PHCpack is a software package for polynomial homotopy continuation, which
provides a robust path tracker [Telen, Van Barel, Verschelde, SISC 2020]. This
tracker computes the radius of convergence of Newton's method, estimates the
distance to the nearest path, and then applies Pad\'{e} approximants to predict
the next point on the path. A priori step size control is less sensitive to
finely tuned tolerances than a posteriori step size control, and is therefore
robust. The Python interface phcpy is extended with a new step-by-step tracker
and is applied to experiment with extrapolation methods to accurately locate
the singular points at the end of solution paths.
