PyCogent is a software library for genomic biology. It is a fully integrated and thoroughly tested framework for: controlling third-party applications; devising workflows; querying databases; conducting novel probabilistic analyses of biological sequence evolution; and generating publication quality graphics. It is distinguished by many unique built-in capabilities (such as true codon alignment) and the frequent addition of entirely new methods for the analysis of genomic data. Knight R, Maxwell P, Birmingham A, Carnes J, Caporaso JG, Easton BC, Eaton M, Hamady M, Lindsay H, Liu Z, Lozupone C, McDonald D, Robeson M, Sammut R, Smit S, Wakefield MJ, Widmann J, Wikman S, Wilson S, Ying H, Huttley GA. Genome Biology, 2007; 8(8):R171.