Kmeans: Between class intertia I'm using KMeans of scikit-learn for clustering of forums.

The attribute inertia_ of model gives the within class inertia but how can i get the between class inertia? In other word how can I verify the quality of my clustering?

Thanks
Total variance = within-class variance + between-class variance.

i.e. if you compute the total variance once, you can get the between class inertia simply by

between-class variance = total variance - within-class variance