The diffpy.Structure package provides objects for storing atomic coordinates, displacement parameters and other crystal structure data. diffpy.Structure supports import and export of structure data in several structure formats such as CIF, PDB, xyz. It provides conversion between fractional and absolute Cartesian coordinates, functions for symmetry expansion from asymmetric unit and generation of symmetry constraints for atom positions and displacement parameters. diffpy.Structure includes definitions of all space groups in over 500 symmetry settings.