Operators, booleans and making decisions

a, b = 17, 5
print(a + b, a - b, a * b)   # 22 12 85
print(a / b)                 # 3.4   true division (always a float)
print(a // b)                # 3     floor division (whole part)
print(a % b)                 # 2     remainder
print(a ** 2)                # 289   power
print(divmod(a, b))          # (3, 2) both at once

minutes = 130
print(f"{minutes // 60} h {minutes % 60} min")

shillings = 2750
print("1000s:", shillings // 1000, "remaining:", shillings % 1000)

total = 100
total += 50    # total = total + 50
total -= 20
total *= 2
total //= 3
print(total)

marks = 67
print(marks >= 50)       # True
print(marks == 100)      # False
print("Nairobi" == "nairobi")  # False: case matters
print(18 <= marks <= 70) # True: Python allows chained comparisons

age = 20
has_id = True
has_ticket = False

print(age >= 18 and has_id)          # both must be True
print(has_ticket or age < 12)        # at least one True
print(not has_ticket)                # reverses

can_enter = age >= 18 and has_id and has_ticket
print("Can enter:", can_enter)

towns = ["Nakuru", "Naivasha", "Gilgil"]
print("Naivasha" in towns)       # True
print("Thika" not in towns)      # True
print("robi" in "Nairobi")       # True: works on text too

x = None
print(x is None)                 # use "is" to check for None

cart = []
if cart:
    print("Checkout")
else:
    print("Your cart is empty")

monthly_income = 45000
existing_loans = 1
credit_score = 640
is_employed = True

eligible = is_employed and monthly_income >= 30000 and existing_loans < 2 and credit_score >= 600
limit = monthly_income * 3 if eligible else 0     # conditional expression

print("Eligible:", eligible)
print(f"Loan limit: KSh {limit:,}")

print(2 + 3 * 4)       # 14
print((2 + 3) * 4)     # 20
print(True or False and False)   # True: "and" runs before "or"

items = []
# Without short-circuiting, items[0] would crash on an empty list:
if items and items[0] > 100:
    print("First item is expensive")
else:
    print("No items, or the first is cheap")

nickname = ""
display = nickname or "Guest"      # or returns the first truthy value
print("Welcome,", display)

count = 0
print(count != 0 and 100 / count)  # safe: division never happens when count is 0

mark = 72
print(50 <= mark < 80)                       # same as 50 <= mark and mark < 80
age = 17
status = "adult" if age >= 18 else "minor"   # one-line if/else (conditional expression)
print(status)

temperature = 31
advice = "Hot: drink water" if temperature > 30 else "Cool" if temperature < 18 else "Pleasant"
print(advice)

def handle(command):
    match command.split():
        case ["balance"]:
            return "Your balance is KSh 3,450"
        case ["send", amount, phone]:
            return f"Sending KSh {amount} to {phone}"
        case ["help" | "menu"]:
            return "Options: balance, send <amount> <phone>"
        case _:
            return "Unknown command"

for c in ["balance", "send 500 0712345678", "menu", "withdraw"]:
    print(c, "->", handle(c))

def fee(amount):
    if amount < 1:
        raise ValueError("Amount must be at least KSh 1")
    elif amount <= 100:
        return 0
    elif amount <= 1_500:
        return 15
    elif amount <= 5_000:
        return 30
    elif amount <= 20_000:
        return 50
    return 100

for a in [50, 100, 101, 1500, 1501, 25000]:
    print(f"KSh {a:>6,}: fee KSh {fee(a)}")