Readable Code

Readable code is debuggable code. The rules are few and earned:

• Names carry the design. retry_count beats n; is_valid_order(order) beats if o[2] == 1 and len(o) > 5.
• Small functions. One screen, one job. If you need "and" to describe what a function does, it is two functions.
• No magic numbers. if score >= 90: — what is 90? GRADE_A_CUTOFF = 90 documents itself.
• Comments explain WHY, not what. # skip header row teaches; # add 1 repeats.

def letter_grade(score):
    if score >= GRADE_A_CUTOFF:
        return "A"
    ...

These habits cost seconds while writing and save hours while debugging — the compound interest of craftsmanship.