The diffpy.srreal package provides calculators for atomic pair distribution function (PDF), bond valence sums (BVS), atom overlaps for a hard-sphere model, bond distances and directions up to specified maximum distance. The atomic structure models are represented with internal classes as non-periodic, periodic or structures with space group symmetries. The package provides implicit adapters from diffpy.structure classes or from Crystal or Molecule objects from pyobjcryst. Adapters can be easily defined for any other structure representations in Python allowing their direct use with the calculators. Calculators support two evaluation models - BASIC, which performs a full pair-summation every time, and OPTIMIZED, which updates only pair contributions that have changed since the last evaluation. Calculations can be split among parallel jobs using Python multiprocessing package or any other library that provides parallel map function. PDF calculations can be done in two modes - either as a real-space summation of peak profiles (PDFCalculator) or as a reciprocal-space Debye summation and Fourier transform of the total scattering structure function (DebyePDFCalculator).