Symmetry-mode analysis is used to detect and characterize structural distortions from pair distribution function data by refining mode amplitudes directly. This approach is successfully applied to a subtle but long-range distortion in TiSe₂ and also to a large but highly localized distortion in MnTe. Two new open-source Python packages, isopydistort and isopytools, were used to carry out this analysis within the open-source DiffPy framework.