Computational thinking (CT), as a new future-oriented literacy, has gained attention at the basic education level. Graphical programming is the common way to develop CT in primary students, but this drag-and-drop programming may weaken students' understanding of programming's abstract concepts and code logic. Text-based programming approaches can solve the problems faced by graphical programming, but few studies have explored the impact of text-based programming on CT. Therefore, we conducted a quasi-experimental study with 98 6th graders to explore the impact of gamified Python programming on CT. The findings showed that CT skills, as well as abstraction and decomposition, pattern recognition and evaluation in CT sub-skills, were significantly higher with students in the experimental group than in the control group. Furthermore, we found that gamified Python programming enabled boys and girls to reach the same level of CT skills. However, in terms of CT sub-skills, we found that gamified Python programming was more beneficial to the development of pattern recognition and evaluation skills for boys and abstraction and decomposition skills for girls. This demonstrated the effectiveness of gamified Python programming to improve primary students' CT skills while clarifying the impact of gender and enriching research in the field of text-based programming.