calculator

# Calculator Do not do multi-step arithmetic in your head — run it. A single wrong digit erodes trust. Use Python for any calculation beyond trivial one-step mental math. ## Quick evaluation ```bash python3 -c "print(2**32 - 1)" python3 -c "print(0.1 + 0.2)" python3 -c "import math; print(math.sqrt(2), math.log(1000, 10))" ``` ## Exact decimal / money (avoid float errors) ```bash python3 -c "from decimal import Decimal as D; print(D('19.99')*D('3'))" ``` ## Percentages, tips, splits ```bash python3 -c "bill=128.50; tip=0.18; n=4; total=bill*(1+tip); print(f'total={total:.2f}, per_person={total/n:.2f}')" ``` ## Stats over a list ```bash python3 -c "import statistics as s; xs=[12,7,9,21,4]; print('mean',s.mean(xs),'median',s.median(xs),'stdev',round(s.pstdev(xs),3))" ``` ## Compound interest ```bash python3 -c "p=10000; r=0.05; n=12; t=3; print(round(p*(1+r/n)**(n*t),2))" ``` ## Guidance - Prefer `decimal.Decimal` for money; prefer `fractions.Fraction` for exact rational results. - Show the user the result, not the code, unless they ask how. - For symbolic algebra/calculus, use `sympy` if available (`python3 -c "import sympy"` to check first). - State units explicitly in the answer when the problem has them.