Summary Table

Principle	You Must	You Should	You Could
[Use Version Control]	Use version control and follow guidance on coding in the open.	Use standard tools (Git & GitHub) to help you version control code.	With your team, agree and design a version control workflow. Use (Git & GitHub) collaboratively and effectively.
[Write Easy to Read Code]	Follow the DHSC adopted style for your language, use meaningful names and avoid overlaps.	Use a linter or code formatter to ensure that your code conforms to the style guide.	Review your code with colleagues to make ensure your names and style promote understanding.
[Correct, Clear, Fast & Concise - In That Order]	Ensure that your code is correct and that it is clear how it functions.	Make your code fast and concise, where possible without sacrificing correctness, clarity or excessive resource! Record choices made to achieve this balance.	Use profiling tools to understand resource usage and refactor to improve clarity and performance.
[Write Flexible Code]	Break up your code into chunks, with a clear structure and don't repeat yourself.	Think about, and document the way your code might break with different inputs. Include input validation to catch mistakes earlier in your code and make it easier to repurpose.	Implement and test thorough error handling. Consider writing and sharing general purposes 'tool' code, especially if you solve a problem someone else might have.
[Comment Effectively]	Write and maintain accurate comments as you code.	Think carefully about why you are leaving comments, what to capture, and what belongs elsewhere (in documentation).	Review old code you have written - are the comments helpful? What would you include next time?
[Document Your Work]	Produce documentation in line with Aqua book guidance.	Assemble documentation as you code.	Use document generation tools to produce documentation.
[Be Demonstrably Correct]	Hold your code to the same standard as any other analysis and record evidence demonstrating it produces the right output.	Use version control to unambiguously link QA to code and outputs and construct automated tests to provide confidence that changes don't break things.	Make a fully automated reproducible analytical pipeline (RAP) which incorporates checks and validation and minimises opportunity for human error.
[Use Sensible Defaults]	Be aware of the defaults, understand why we have them and follow them unless you can explain how the benefits of an alternative approach outweigh those of consistency.	Help define what the defaults should be, and actively participate in discussion and debate to keep them up to date and relevant.	Proactively review and compare the defaults used with the way you work.
[Be Reproducible]	Keep track of what you have done and document it unambiguously so that someone else can recreate it.	Write portable code, in a standard project structure so that it is easy for someone else to run it.	Turn your code into a package / library / module, learn and promote RAP techniques, or use containers to achieve reproducibility.
[Use Appropriate and Tidy Data]	Know what 'Tidy Data' is, and understand why it is valuable.	Be familiar with the data types and structures available to you and ensure that you use the right ones.	Think about relationships between datasets, design schemas and store data in an efficient way.