Lesson 6 — Operations

Operators

Python operators include some Java/C# don't have as language keywords: // for floor division, ** for power, and and/or/not instead of symbols.

PYTHON — Arithmetic 
a, b = 17, 5
print(a + b)    # 22
print(a - b)    # 12
print(a * b)    # 85
print(a / b)    # 3.4 — always float in Python 3
print(a // b)   # 3   — floor division (truncates)
print(a % b)    # 2   — remainder
print(a ** 2)   # 289 — power (no Math.pow needed)

# Integer division pitfall from Java/C#: NOT an issue in Python 3
# Python 3: 7 / 2 == 3.5 (use // for integer division)

Logical Operators — Words not Symbols

Python uses English words for logical operators, not symbols like Java's && and ||. This makes conditions read like English.

PYTHON — Logical operators 
age = 22
has_matric  = True
has_laptop  = False

# and, or, not — not &&, ||, !
if age >= 18 and has_matric:
    print("Eligible for the programme")

if has_laptop or age > 20:
    print("Can attend in-person or remotely")

if not has_laptop:
    print("Please request a loaned device")

# Short-circuit: Python stops as soon as outcome is determined
result = False and heavy_computation()  # heavy_computation() never called
result = True  or heavy_computation()  # heavy_computation() never called

Identity and Membership

PYTHON — Identity and membership 
courses = ["Java", "Python", "SQL"]

# in — membership test (works on lists, strings, dicts, sets, tuples)
print("Python" in courses)   # True
print("Kotlin" in courses)   # False
print("P" in "Python")       # True

# is — identity (same object in memory)
# Use only for None checks, not equality:
x = None
if x is None:
    print("x is None")

# is vs ==:
a = [1, 2, 3]
b = [1, 2, 3]
print(a == b)    # True  — same value
print(a is b)    # False — different objects

c = a
print(a is c)    # True  — same object

Augmented Assignment

PYTHON — Augmented assignment 
score = 50
score += 10  # 60
score -= 5   # 55
score *= 2   # 110
score //= 11 # 10
score **= 2  # 100
print(score)  # 100

Practice Task

Your Turn

Given marks 65, 72, 80 as ints: (1) calculate average with / — is it a float? (2) use // to get the integer average, (3) use % to check if the total is divisible by 3, (4) use ** to compute the product of all three marks to the power of 1/3 (the geometric mean), (5) check if all three are above 60 with a single and expression.

Common Mistakes

  • / always returns float in Python 3 — use // for integer division.
  • and/or not &&/|| — the Java/C# symbols are not logical operators in Python.
  • is for identity, == for value equality — never use is for comparing strings or numbers.
  • ** is power, not XOR — ^ is bitwise XOR in Python.

Professional Tip

The in operator is one of Python's best features. Checking membership in a list is O(n), in a set is O(1). When performance matters for membership tests, use a set.

Mini Quiz

What does the // operator do in Python?