Py Boy Scout

The Boy Scout Rule

"Always leave the campground cleaner than you found it." — Robert Baden-Powell

"Always check a module in cleaner than when you checked it out." — Robert C. Martin, Clean Code

The Philosophy

You don't have to make every module perfect. You simply have to make it a little bit better than when you found it.

If we all followed this simple rule:

• Our systems would gradually get better as they evolved
• Teams would care for the system as a whole
• The relentless deterioration of software would end

When Working on Code

Every time you touch code, look for at least one small improvement:

Quick Wins (Do These Immediately)

• Rename a poorly named variable → triggers py-clean-names
• Delete a redundant comment → triggers py-clean-comments
• Remove dead code or unused imports
• Replace a magic number with a named constant
• Extract a deeply nested block into a well-named function

Deeper Improvements (When Time Allows)

• Split a function that does multiple things → triggers py-clean-functions
• Remove duplication (DRY) → triggers py-clean-general
• Add missing boundary checks
• Improve test coverage → triggers py-clean-tests

The Rule in Practice

# You're asked to fix a bug in this function:
def proc(d, x, flag=False):
    # process data
    for i in d:
        if i > 0:
            if flag:
                x.append(i * 1.0825)  # tax
            else:
                x.append(i)
    return x

# Don't just fix the bug and leave.
# Leave it cleaner:
TAX_RATE = 0.0825

def process_positive_values(
    values: list[float],
    apply_tax: bool = False
) -> list[float]:
    """Filter positive values, optionally applying tax."""
    rate = 1 + TAX_RATE if apply_tax else 1
    return [v * rate for v in values if v > 0]

What changed:

• ✅ Descriptive function name (N1)
• ✅ Clear parameter names (N1)
• ✅ Type hints (P3)
• ✅ Named constant for magic number (G25)
• ✅ No output argument mutation (F2)
• ✅ Useful docstring (C4)

Skill Orchestration

This skill coordinates with specialized skills based on what you're doing:

The Mindset

Don't:

• Leave code worse than you found it
• Say "that's not my code"
• Wait for a dedicated refactoring sprint
• Make massive changes unrelated to your task

Do:

• Make one small improvement with every commit
• Fix what you see, even if you didn't break it
• Keep changes proportional to your task
• Leave a trail of quality improvements

AI Behavior

When working on code:

1. Complete the requested task first
2. Identify at least one small cleanup opportunity
3. Apply the appropriate specialized skill
4. Note the improvement made (e.g., "Also cleaned up: renamed x to results for clarity")

When reviewing code:

1. Load python-clean-code for comprehensive rule checking
2. Flag violations by rule number
3. Suggest incremental improvements, not complete rewrites

The Boy Scout Promise

Every piece of code you touch gets a little better. Not perfect—just better.

Over time, better compounds into excellent.