Here are the source code for the Generalized Parton Distributions through Universal Moment Parameterization (GUMP) program for global analysis of GPDs.
For GPDs calculations:
The Predictions.py file contains examples of generating PDFs and GPDs with GUMP parameters, which are obtained with the fitting program and stored in params.csv under the folder GUMP_Params.
Caveat: the GPD evaluation can be slow since it involves QCD evolution in moment space and numerical contour integral to get back to x space.