Project 4 — Unit Converter

Convert between common units (length, weight, temperature) using a menu-driven CLI. Extend the conversion table with new units without changing the core logic.

dictfunctionmenuconversion

Duration

⏱ 1.5 hours

Level

📊 Basic Applied

Prerequisite

🎯 Basic Weeks 7, 9

OUTCOME

A data-driven unit converter that is easy to extend

What you'll learn

1Store conversion factors in a dict-of-dict structure
2Write a generic convert(value, from_unit, to_unit) function
3Present a clean numbered menu
4Handle temperature as a special case (formula-based)

Supported Units

Category	Units
Length	mm, cm, m, km, in, ft, mi
Weight	mg, g, kg, lb, oz
Temperature	°C, °F, K

Sample Session

text

Unit Converter
1) Length  2) Weight  3) Temperature  4) Quit
Choice: 1
From unit (mm/cm/m/km/in/ft/mi): km
To unit: mi
Value: 5
5 km = 3.1069 mi

Choice: 3
From unit (C/F/K): C
To unit: F
Value: 100
100°C = 212.0°F

💻 Examples

Run these examples and check the output yourself.

solution.py— Data-driven unit converter

CODE

# All conversions to SI base unit (metre, gram, kelvin)
LENGTH = {"mm":1e-3,"cm":1e-2,"m":1,"km":1e3,"in":0.0254,"ft":0.3048,"mi":1609.344}
WEIGHT = {"mg":1e-3,"g":1,"kg":1e3,"lb":453.592,"oz":28.3495}

def convert_linear(value, from_u, to_u, table):
    return value * table[from_u] / table[to_u]

def convert_temp(value, from_u, to_u):
    # Convert to Kelvin first
    if from_u == "C": k = value + 273.15
    elif from_u == "F": k = (value - 32) * 5/9 + 273.15
    else: k = value
    if to_u == "C": return k - 273.15
    if to_u == "F": return (k - 273.15) * 9/5 + 32
    return k

while True:
    print("\n1) Length  2) Weight  3) Temperature  4) Quit")
    c = input("Choice: ").strip()
    if c == "4": break
    elif c == "1": tbl = LENGTH; cat = "Length"
    elif c == "2": tbl = WEIGHT; cat = "Weight"
    elif c == "3":
        from_u = input(f"From (C/F/K): ").upper()
        to_u = input(f"To (C/F/K): ").upper()
        val = float(input("Value: "))
        print(f"{val}°{from_u} = {convert_temp(val,from_u,to_u):.4f}°{to_u}")
        continue
    else: print("Invalid"); continue
    units = list(tbl.keys())
    from_u = input(f"From unit ({"/".join(units)}): ").lower()
    to_u = input(f"To unit: ").lower()
    val = float(input("Value: "))
    result = convert_linear(val, from_u, to_u, tbl)
    print(f"{val} {from_u} = {result:.6g} {to_u}")

📝 Exercises

Try them yourself first, then open the solution to compare.

Exercise 1

Build the unit converter

Goal: Implement the converter with length, weight, and temperature categories.

Requirements

Data-driven design (dicts for length and weight)
Temperature handled via formula
Handles unknown units gracefully
Loop until quit

Example code / lecture materials

All lecture materials and example code are openly available on GitHub.

View on GitHub ↗