# 3.6. kwant.operator – Operators and Observables¶

## Observables¶

 Density(syst[, onsite, where, …]) An operator for calculating general densities. Current(syst[, onsite, where, …]) An operator for calculating general currents. Source(syst[, onsite, where, …]) An operator for calculating general sources.

kwant.solvers.mumps – High performance sparse solver based on MUMPS