NeuroKit2: The Python Toolbox for Neurophysiological Signal Processing. This is an adaptation of NK2 to take RRIs or peak times from fetal and maternal heart rate data as input and output 62 HRV measures including optimal time delay-based complexity measures with user-definable time window length.
NK's documentation is extensive. I attempted to simplify things here summarizing all you need to produce the most extensive HRV estimation output into one place. The resulting notebook should allow you to run similar analyses quickly and at scale on similar time-series data.
Huge thanks to the team of neurokit!