The Python 3 language is described: data types, operators, conditions, loops, regular expressions, functions, object-oriented programming tools, working with files and directories, standard library modules. Particular attention is paid to the PyQt library, which allows you to create applications with a graphical interface. Tools for processing signals and events, managing window properties, developing multi-threaded applications are considered; the main components (buttons, fields, etc.), tools for working with databases, multimedia, printing documents and exporting them are described. The publisher's website provides examples from the book. The second edition describes the current versions of Python 3.6.3 and PyQt 5.9.2, tools for interacting with Windows and saving application settings, and discusses the process of developing a full-featured application.