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As Scratch has become one of the most popular educational programming languages, understanding its common programming idioms can benefit both computing educators and learners. This understanding can fine-tune the curricular development to help learners master the fundamentals of writing idiomatic code in their programming pursuits. Unfortunately, the research community’s understanding of what constitutes idiomatic Scratch code has been limited. To help bridge this knowledge gap, we systematically identified idioms as based on canonical source code, presented in widely available educational materials. We implemented a tool that automatically detects these idioms to assess their prevalence within a large dataset of over 70K Scratch projects in different experience backgrounds and project categories. Since communal learning and the practice of remixing are one of the cornerstones of the Scratch programming community, we studied the relationship between common programming idioms and remixes. Having analyzed the original projects and their remixes, we observed that different idioms may associate with dissimilar types of code changes. Code changes in remixes are desirable, as they require a meaningful programming effort that spurs the learning process. The ability to substantially change a project in its remixes hinges on the project’s code being easy to understand and modify. Our findings suggest that the presence of certain common idioms can indeed positively impact the degree of code changes in remixes. Our findings can help form a foundation of what comprises common Scratch programming idioms, thus benefiting both introductory computing education and Scratch programming tools. 

As a popular language for teaching introductory programming, Java can profoundly influence beginner programmers with its coding style and idioms. Despite its many advantages, the paradigmatic coding style in Java is often described as verbose. As a result, when writing code in more concise languages, such programmers tend to emulate the familiar Java coding idioms, thus neglecting to take advantage of the more succinct counterparts in those languages. As a result of such verbosity, not only the overall code quality suffers, but the verbose non-idiomatic patterns also render code hard to understand and maintain. In this paper, we study the incidences of Java-like verbosity as they occur in Python codebases. We present a collection of Java-Like Verbosity Anti-patterns and our pilot study of their presence in representative open-source Python codebases. We discuss our findings as a call for action to computing educators, particularly those who work with introductory students. We need novel pedagogical interventions that encourage budding programmers to write concise idiomatic code in any language. 

As quality problems plague the modern society's software infrastructure, a fundamental learning objective of computing education has become developing students' attitudes, knowledge, and practices centered around software quality. Teaching software quality and its disciplined practices has thus far been limited to more advanced courses, due to the prevailing assumptions about the introductory learner's unpreparedness for the topic and potential negative impacts on learner motivation. In this paper, we present empirical evidence that starkly contradicts the established conventional belief. Specifically, by exploring how novice programmers learn to refactor code duplication with and without automated tools, we found strong evidence that novices grasp the importance of code quality and its improvement. This empirical evidence motivated us, in retrospect, to closely examine the design of our online interactive tutorial, a platform that drove our experimental user study. We identify and discuss the tutorial's key design principles and affirm their efficacy based on the observed learning experiences. The obtained insights can inform curricular interventions that introduce introductory students to code quality and its disciplined improvement practices. 

Block-based programming has been overwhelmingly successful in revitalizing introductory computing education and in facilitating end-user development. However, poor code quality makes block-based programs hard to understand, modify, and reuse, thus hurting the educational and productivity effectiveness of blocks. There is great potential benefit in empowering programmers in this domain to systematically improve the code quality of their projects. Refactoring--improving code quality while preserving its semantics--has been widely adopted in traditional software development. In this work, we introduce refactoring to Scratch. We define four new Scratch refactorings: Extract Custom Block, Extract Parent Sprite, Extract Constant, and Reduce Variable Scope. To automate the application of these refactorings, we enhance the Scratch programming environment with powerful program analysis and transformation routines. To evaluate the utility of these refactorings, we apply them to remove the code smells detected in a representative dataset of 448 Scratch projects. We also conduct a between-subjects user study with 24 participants to assess how our refactoring tools impact programmers. Our results show that refactoring improves the subjects' code quality metrics, while our refactoring tools help motivate programmers to improve code quality.