This work delves into the field of code clone detection, focusing on Python programming language. We are interested in finding Stack Overflow snippets in real projects. The main goal of this work is to evaluate the influence of copy-and-paste programming on the overall quality of a software project. The NiCad clone detector is used to detect similar code fragments. Additionally, modification of this tool is presented in order to improve the detection process. Code quality is assessed by the volume of duplicate code and by the number of reported issues. The impact is evaluated on a sample of open-source projects hosted on GitHub. We perform a series of statistical hypothesis tests and conclude that there is a~correlation between source code quality and the presence of Stack Overflow snippet in the code base.