Clean Code Principles

# ❌ BAD: Hard to read
def p(d,t):
    r=d/t
    return r

# ✅ GOOD: Self-documenting
def calculate_speed(distance_km: float, time_hours: float) -> float:
    """Calculate speed in km/h."""
    if time_hours <= 0:
        raise ValueError("Time must be positive")
    return distance_km / time_hours

# ❌ BAD: Magic numbers
def calc(amount):
    return amount * 0.18
    
# ✅ GOOD: Named constants  
TAX_RATE = 0.18

def calculate_tax(amount: float) -> float:
    """Calculate tax based on the standard rate."""
    return amount * TAX_RATE

# ❌ BAD: Long function doing many things
# ✅ GOOD: Small, focused functions
def validate_email(email):
    return "@" in email and "." in email

def format_user(name, email):
    return {"name": name.title(), "email": email.lower()}

def process_registration(name, email):
    if not validate_email(email):
        return {"error": "Invalid email"}
    user = format_user(name, email)
    return {"success": True, "user": user}

# Demo
result = process_registration("alice smith", "Alice@Email.COM")
print(f"Result: {result}")

# Clean code principles:
print("\n=== Clean Code Principles ===")
principles = [
    "Use descriptive names (user_age, not x)",
    "Keep functions short (one responsibility)",
    "Avoid magic numbers (use constants)",
    "Write docstrings for public functions",
    "DRY — Don't Repeat Yourself",
    "KISS — Keep It Simple, Stupid",
    "Handle errors explicitly",
    "Use type hints for clarity",
]
for p in principles:
    print(f"  • {p}")