I used Circos quite a lot back in time. It's written in Perl. I was working on a Python visualization tool for analyzing the relationships between different IP, from network traffic capture:

https://github.com/cedricbonhomme/IP-Link

(there is a link to the documentation with some nice chord diagrams.) This one is quite impressive: https://github.com/cedricbonhomme/IP-Link/blob/master/docs/_... nut not easy to read !