YALTAPy is a Python toolbox dedicated to the stability analysis of (possibly fractional) delay systems with commensurate delays given by their transfer function. The questions YALTA and YALTAPy can answer are: - In the case of neutral systems - Find the position of asymptotic axes. - If the imaginary axis is asymptotic axis, find if the asymptotic poles of the chain are left or right the imaginary axis. - In the case of retarded systems or of neutral systems with asymptotic axes in ${\mathrm{Re}(s) < 0}$, find: - For a given delay, the number and the position of unstable poles. - For which values of the delay the system is stable. - For a set of values of the delay, the position of unstable poles (root locus). - Find (for non fractional systems) the coprime factors (N, D) of the transfer function as well as an approximation ($N_n$, $D_n$) in $H_\infty$-norm