The overall interview process included three steps: phone screening, and two on-site meetings on different dates.
Phone screening included several very basic technical questions in CS in order to filter out any irrelevant candidates. A few Python-specific questions were asked as well.
First on-site interview was entirely technical. A team of three people attended the interview from the company side, two of them co-founders and another one a Python developer.
Two main tasks were given, none of which implied knowledge of any specific programming language. A candidate had to come up with algorithms effectively solving each of the given tasks. That was followed up by the complexity questions and implementation of core parts of the suggested algorithms. A few minor questions checking Python knowledge summed up the interview.
Only one of the beforementioned co-founders started a second interview round. More abstract task was given, requiring another algorithmic solution, which was subjectively difficult for a person without a strong academic background such as myself. Nevertheless, with the interviewer's help the question had been eventually solved and once again, followed up by the implementation part.
Then, with the presence of CEO in the room, a personal interview had begun. It ended with a salary discussion and a job offer.
P.S. Currently taking part in the interviewing and mentoring processes of the company, I have to mention, that those have changed over time, but the general approach remained: more algorithmic tasks, less language- or technology-specific questions.
