# 3.2. kwant.builder – High-level construction of systems¶

## Types¶

 Builder([symmetry, conservation_law, …]) A tight binding system defined on a graph. Site(family, tag[, _i_know_what_i_do]) A site, member of a SiteFamily. HoppingKind(delta, family_a[, family_b]) A pattern for matching hoppings. SimpleSiteFamily([name, norbs]) A site family used as an example and for testing. BuilderLead(builder, interface[, padding]) A lead made from a Builder with a spatial symmetry. SelfEnergyLead(selfenergy_func, interface, …) A general lead defined by its self energy. ModesLead(modes_func, interface, parameters) A general lead defined by its modes wave functions. FiniteSystem(builder) Finalized Builder with leads. InfiniteSystem(builder[, interface_order]) Finalized infinite system, extracted from a Builder.

## Abstract base classes¶

 SiteFamily(canonical_repr, name, norbs) Abstract base class for site families. Abstract base class for spatial symmetries. Abstract base class for leads that can be attached to a Builder.