The thesis aims to create a tool for detecting code quality defects in Python code written by novice programmers (e.g., students of introductory programming courses or users of online learning platforms). The tool should detect various stylistic and structural defects, such as using a while loop instead of a for loop, conditions that can be simplified using logical operators, use of global variables, unreachable code or code with no effect, and similar. The tool should provide a reasonable default configuration specifying which defects will be reported and a convenient way to alter the configuration, even on a per-file basis. All the configuration options should be documented. It should be possible to run the tool from the command line to allow for possible integration into other tools. The tool should also provide a web interface so that students can easily interact with it. The site should display detected defects, their explanations and related code examples. Evaluation of the detectors should be a part of the thesis.