Operators and Expressions

Arithmetic Operators

a, b = 10, 3

print(a + b)   # 13  — addition
print(a - b)   # 7   — subtraction
print(a * b)   # 30  — multiplication
print(a / b)   # 3.3333... — true division (always float)
print(a // b)  # 3   — floor division (integer result)
print(a % b)   # 1   — modulo (remainder)
print(a ** b)  # 1000 — exponentiation

Comparison Operators

x, y = 5, 10

print(x == y)   # False — equal
print(x != y)   # True  — not equal
print(x < y)    # True  — less than
print(x > y)    # False — greater than
print(x <= 5)   # True  — less than or equal
print(x >= 5)   # True  — greater than or equal

Comparisons return True or False.

Logical Operators

a = True
b = False

print(a and b)   # False — both must be True
print(a or b)    # True  — at least one must be True
print(not a)     # False — negation

# Short-circuit evaluation:
print(False and 1/0)   # False (1/0 never evaluated)
print(True or 1/0)     # True  (1/0 never evaluated)

Truthy Logical Returns

# 'and' returns first falsy value, or last value
print(0 and 5)      # 0
print(3 and 5)      # 5
print("" and "hi")  # ""

# 'or' returns first truthy value, or last value
print(0 or 5)       # 5
print(3 or 5)       # 3
print("" or "hi")   # "hi"

Assignment Operators

x = 10

x += 5   # x = x + 5  → 15
x -= 3   # x = x - 3  → 12
x *= 2   # x = x * 2  → 24
x /= 4   # x = x / 4  → 6.0
x //= 2  # x = x // 2 → 3.0
x **= 3  # x = x ** 3 → 27.0
x %= 5   # x = x % 5  → 2.0

Membership Operators

fruits = ["apple", "banana", "cherry"]

print("apple" in fruits)      # True
print("grape" not in fruits)  # True
print("x" in "Python")        # True — works on strings too

Identity Operators

a = [1, 2, 3]
b = a           # same object
c = [1, 2, 3]   # different object, same value

print(a is b)   # True  — same identity (same object in memory)
print(a is c)   # False — different objects
print(a == c)   # True  — same value

# Use 'is' only to compare to None:
x = None
print(x is None)    # True  (preferred over x == None)

Bitwise Operators

a = 0b1010   # 10
b = 0b1100   # 12

print(a & b)   # 0b1000  = 8  — AND
print(a | b)   # 0b1110  = 14 — OR
print(a ^ b)   # 0b0110  = 6  — XOR
print(~a)      # -11           — NOT (complement)
print(a << 1)  # 20            — left shift
print(a >> 1)  # 5             — right shift

Operator Precedence

From highest to lowest:

1. () — parentheses
2. ** — exponentiation
3. +x, -x, ~x — unary
4. *, /, //, %
5. +, -
6. <<, >>
7. &, ^, |
8. Comparison: ==, !=, <, >, etc.
9. not
10. and
11. or

result = 2 + 3 * 4 ** 2 - 1   # 2 + 3*16 - 1 = 49
print(result)  # 49

Exercises

Exercise 1: Arithmetic

Write a program that calculates and prints:

• The area of a circle with radius 7 (use 3.14159)
• The remainder when 2**32 is divided by 1000

Solution:

radius = 7
area = 3.14159 * radius ** 2
print(f"Area: {area:.2f}")      # 153.94

remainder = 2**32 % 1000
print(f"Remainder: {remainder}")  # 296

Exercise 2: Even or Odd

Using only the modulo operator, determine if 127 is even or odd.

Solution:

n = 127
is_even = n % 2 == 0
print("Even" if is_even else "Odd")  # Odd

Exercise 3: Chained Comparison

Python supports chained comparisons. Predict the output:

x = 5
print(1 < x < 10)
print(1 < x < 4)
print(x == 5 == 5.0)

Solution:

True   # 1 < 5 AND 5 < 10
False  # 1 < 5 AND 5 < 4 → False
True   # 5 == 5 AND 5 == 5.0

Exercise 4: Swap with XOR

Swap two variables using only XOR (bitwise) without a temp variable.

Solution:

a = 15
b = 27
a = a ^ b
b = a ^ b
a = a ^ b
print(a, b)  # 27 15