There are plenty of 'pretty-printing' visualization libraries for Javascript. E.g. those listed here.
Googling for 'python visualization libraries' only turns up stuff like VTK and mayavi, which are primarily more for no-nonsense scientific use.
So, do you know of any Python libraries similar to those Javascript ones in the above link? I particularly like the Javascript Infovis Toolkit.
For Python there really isn't "one viz library to rule them all". There are different libraries and toolkits for different purposes. For graphs in Python you may find igraph useful. For other types of scientific or data visualizations matplotlib is also good.