PPM(Prediction by partial matching) is a compression algorithm which has several variations of implementations. PPMd is the implementation by Dmitry Shkarin. It is used in the RAR and by 7-Zip as one of several possible methods.

ppmd, aka. ppmd-cffi, is a python bindings with PPMd implementation by C language. The C codes are derived from p7zip, portable 7-zip implementation. ppmd-cffi support PPMd ver.H and PPMd ver.I.