Operators and Expressions

1. Introduction to Operators

An operator is a symbol that tells the compiler or interpreter to perform a specific mathematical, relational, or logical operation on one or more operands.

Python provides the following categories of operators:

2. Arithmetic Operators

a, b = 15, 4
print(a + b)   # 19
print(a - b)   # 11
print(a * b)   # 60
print(a / b)   # 3.75
print(a // b)  # 3 (floor division)
print(a % b)   # 3 (remainder)
print(a ** b)  # 50625 (15^4)

3. Relational (Comparison) Operators

Relational operators compare two values and return a boolean result (True or False).

4. Logical Operators

Logical operators combine conditional statements.

marks = 85
attendance = 90
if marks >= 80 and attendance >= 75:
    print("Eligible for exam")

5. Assignment Operators

The = operator assigns a value to a variable.

x = 10     # Simple assignment
y = x + 5 # Expression assignment
a = b = c = 20  # Chained assignment
p, q, r = 1, 2, 3  # Multiple assignment

6. Augmented Assignment Operators

These operators combine an arithmetic operation with assignment.

7. Bitwise Operators

Bitwise operators perform operations on binary representations of integers.

8. Identity Operators

Identity operators check whether two objects are the same object (same memory location).

a = [1, 2, 3]
b = [1, 2, 3]
c = a

print(a is c)     # True (same object)
print(a is b)     # False (different objects)
print(a is not b) # True
print(a == b)     # True (same value)

9. Membership Operators

Membership operators test whether a value is present in a sequence.

fruits = ["apple", "banana", "cherry"]
print("apple" in fruits)     # True
print("grape" not in fruits) # True

text = "Hello, World!"
print("World" in text)       # True

10. Operator Precedence

Operator precedence determines the order in which operators are evaluated in an expression. Higher precedence operators are evaluated first.

result = 5 + 3 * 2 ** 2  # 5 + 3 * 4 = 5 + 12 = 17
result2 = (5 + 3) * 2 ** 2  # 8 * 4 = 32

11. Associativity

When operators have the same precedence, associativity determines the order of evaluation.

• Most operators have left-to-right associativity.
• Exponentiation (**) has right-to-left associativity.

# Left to right
print(10 - 5 - 2)   # (10 - 5) - 2 = 3
print(10 / 5 * 2)   # (10 / 5) * 2 = 4.0

# Right to left (exponentiation)
print(2 ** 3 ** 2)  # 2 ** (3 ** 2) = 2 ** 9 = 512

12. Expressions and Evaluation

An expression is a combination of values, variables, operators, and function calls that evaluates to a single value.

# Arithmetic expressions
area = 3.14 * radius ** 2
average = (a + b + c) / 3

# Boolean expressions
is_pass = marks >= 33
can_vote = age >= 18 and citizenship == "Indian"

# Mixed expressions
result = 10 + 20 * 3 - 5 / 2  # 10 + 60 - 2.5 = 67.5