I've never heard of it.

I have written Python for 10 years on and off and have never come across it, or if I did I had forgotten about it.

This is not the same thing. Hacker News as a website is catered to an audience that is mostly familiar with programming. I would say it's safe to assume for any given visitor that they are probably aware of basic computing and programming terminology, but not that they would know what "NetworkX" means.

The new title is fitting (it specifies what it's a Python library now).