Since many future energy technologies, such as power generation with carbon-free hydrogen, biogas, and carbon capture, require sophisticated gas separation processes, many studies have investigated pressure swing adsorption (PSA) processes due to their low cost and good energy efficiency. In the investigation of the PSA processes, process simulations based on commercial software tools and in-house models have been conducted with different approaches. Although these approaches have good simulation performances in particular cases, the use of software and in-house models is limited owing to certain drawbacks. The primary drawbacks include the high barriers to entry because of the need for excessive prior knowledge and non-compatibility with other software tools. Thus, in this study, an open-source python-based adsorption process evaluation package (pyAPEP) was proposed for the simulation of PSA process. The pyAPEP comprises three modules: ▪, ▪, and ▪. The ▪ module determines the optimal isotherm models for process simulations from the given adsorption equilibrium data. ▪ and ▪ are the modules for ideal and actual PSA process simulations, respectively, and they help users perform the process simulations easily using simple prior knowledge. This study also introduces the theories and methods in pyAPEP package, and it summarizes the example codes for each module. Finally, the applicability of the proposed package is demonstrated through practical example problems.Source code: https://github.com/sebygaa/pyAPEP or https://github.com/NahyeonAn/pyAPEPDocumentation: https://sebygaa.github.io/pyAPEP or https://nahyeonan.github.io/pyAPEP