Homework: Tip Calculator

作业: 小费计算器

≈ 40 min · python-functions · Open in WolfCode

Four functions. Three small helpers and one orchestrator. The grade is for decomposition as much as correctness.

The four functions

compute_tip(subtotal, tip_pct) — tip amount
compute_total(subtotal, tip_pct) — subtotal + tip
split_evenly(amount, people) — per-person share
bill_summary(subtotal, tip_pct, people) — dict with all three

The right shape

See how each helper does ONE thing

def compute_tip(subtotal, tip_pct):
    return subtotal * tip_pct / 100

def compute_total(subtotal, tip_pct):
    return subtotal + compute_tip(subtotal, tip_pct)    # composition

def split_evenly(amount, people):
    return amount / people

def bill_summary(subtotal, tip_pct, people):
    tip = compute_tip(subtotal, tip_pct)
    total = compute_total(subtotal, tip_pct)
    per_person = split_evenly(total, people)
    return {
        "tip": round(tip, 2),
        "total": round(total, 2),
        "per_person": round(per_person, 2),
    }

print(bill_summary(50.00, 20, 4))
print(bill_summary(125.50, 18, 3))

Loading Python runtime (~5 MB, one-time)…

Why FOUR functions instead of one?

You could write everything in one bill_summary. It would work. But three things would suffer:

Tip formula is computed multiple times — change it once, find it three places.
Each line does too much — hard to test pieces in isolation.
Names disappear — readers re-parse the arithmetic instead of trusting compute_tip.

Acceptance criteria

All 7 tests pass
compute_total CALLS compute_tip
bill_summary CALLS at least 2 of the 3 helpers
Dict values rounded to 2 decimals