The SIMEX platform is a start-to-end simulation platform for experiments at advanced laser and X-ray light sources. It provides a complete set of tools simulating the X-ray from the source to the detector. SimEx-Lite is the lightweight python API of the SIMEX platform, based on the libpyvinyl package to provide the users with the flexibility to install the simulation in various software environments, easy usage, and extensibility. This simulation platform has been used in the research projects of the effects of water layers and detector noises in single-particle imaging experiments, and in the guidance of detector setup in user experiments. Its further applications in the research of the XFEL source and wavefront propagation, and in the coupling with machine learning are in exploration.