# 3.1. kwant – Top level package¶

For convenience, short names are provided for a few widely used objects from the sub-packages. Otherwise, this package has only very limited functionality of its own.

## Generic functionality¶

kwant.__version__ = '1.5.0a0.dev103+ge154dc0'[source]

The version of Kwant is available under the name __version__.

This string respects PEP 440 and has the following format

• Released version: ‘1.3.0’, ‘1.3.1’, etc.

• Alpha version: ‘1.2.0a0’, ‘1.2.0a1’, etc.

• Beta version: ‘1.1.0b0’, ‘1.1.0b1’, etc.

• Development version (derived from git describe --first-parent --dirty): ‘1.3.2.dev27+gdecf6893’, ‘1.1.1.dev10+gabcd012.dirty’, etc.

• Development version with incomplete information: ‘unknown’, ‘unknown+g0123abc’, etc.

 KwantDeprecationWarning Class of warnings about a deprecated feature of Kwant. UserCodeError Class for errors that occur in user-provided code.

## From kwant.builder¶

 Builder([symmetry, conservation_law, …]) A tight binding system defined on a graph. HoppingKind(delta, family_a[, family_b]) A pattern for matching hoppings.

## From kwant.lattice¶

 TranslationalSymmetry(*periods) A translational symmetry defined in real space.

## From kwant.plotter¶

 plot(sys[, num_lead_cells, unit, …]) Plot a system in 2 or 3 dimensions.

## From kwant.solvers.default¶

 greens_function(sys[, energy, args, …]) Compute the retarded Green’s function of the system between its leads. ldos(sys[, energy, args, check_hermiticity, …]) Calculate the local density of states of a system at a given energy. smatrix(sys[, energy, args, out_leads, …]) Compute the scattering matrix of a system. wave_function(sys[, energy, args, …]) Return a callable object for the computation of the wave function inside the scattering region.