This paper presents the development of a computer tool for studying the impact of In-Motion Charging (IMC) and Opportunity Charging (OC) for Electric Buses (EBs) in distribution systems. This tool is developed as a Python code that computes several operational bus fleet parameters, including speed, position, power, energy consumption and battery State of Charge (SoC) during an operating day. A Graphical User Interface (GUI) is also developed to facilitate simulation data input, output visualization, and distribution system impact analysis configuration, which is performed externally with OpenDSS software. A study case that analyzes the electrification of a bus service route in Barranquilla, Colombia, its possible impacts on a distribution feeder's voltages and currents, as well as the SoC of the EB batteries, is presented to demonstrate the capabilities of the proposed tool.