The development of technological progress makes increased demands on the strength properties of structural elements of buildings and structures, machines and mechanisms, and a decrease in their material consumption. This leads to the need for effective use of existing and creation of new methods of solid mechanics and the training of new highly qualified specialists. Additionally, having control over the objects' sizes will allow potential users (designers, engineers etc.) to consider the desired properties in the optimization problem. Otherwise, it would be both quite difficult and inefficient to utilize. This article describes a system for CAD modelling. Its implementation is based on open-source software, such as Python programming language, Jupyterlab and FEniCS library. The system also supports topological optimization and allows its user to integrate the desired numerical methods, which is currently not supported in the existing solutions. The execution time of solving the example problem was measured and presented together with the result. Special attention was paid to the comparison of the described solution with the currently existing ones.