Python Operators

Python Operators: Expression Evaluation & Precedence

Operators are special symbols that perform computations on operands. Python categorizes operators into arithmetic, comparison, logical, bitwise, assignment, membership, and identity operators.

Operator Categories & Precedence

flowchart TD
    A["Highest Precedence"] --> B["Parentheses ()"]
    B --> C["Exponentiation **"]
    C --> D["Unary Operators +x, -x, ~x"]
    D --> E["Multiplicative *, /, //, %"]
    E --> F["Additive +, -"]
    F --> G["Bitwise Shifts <<, >>"]
    G --> H["Bitwise AND &, XOR ^, OR |"]
    H --> I["Comparison & Membership ==, !=, in, is"]
    I --> J["Logical NOT, AND, OR"]
    J --> K["Lowest Precedence: Assignment =, +=, -="]

Practical Code Example

from typing import List

def demonstrate_operators() -> None:
    # Arithmetic & Floor Division
    total_items = 27
    batch_size = 5
    full_batches = total_items // batch_size  # 5
    remainder = total_items % batch_size      # 2
    print(f"Batches: {full_batches}, Remainder: {remainder}")

    # Bitwise Operations (Flags)
    READ_PERMISSION = 1 << 0   # 1 (0001)
    WRITE_PERMISSION = 1 << 1  # 2 (0010)
    EXEC_PERMISSION = 1 << 2   # 4 (0100)

    user_permissions = READ_PERMISSION | WRITE_PERMISSION  # 3 (0011)
    has_write = bool(user_permissions & WRITE_PERMISSION)
    has_exec = bool(user_permissions & EXEC_PERMISSION)
    print(f"Permissions Flag: {user_permissions} | Write: {has_write} | Exec: {has_exec}")

    # Membership & Identity Operators
    numbers: List[int] = [10, 20, 30]
    print(f"20 in numbers: {20 in numbers}")
    print(f"40 not in numbers: {40 not in numbers}")

if __name__ == "__main__":
    demonstrate_operators()

Best Practices & Gotchas

• Exponentiation Precedence: -3 ** 2 evaluates to -9 because ** binds tighter than unary -. Use (-3) ** 2 for 9.
• Chained Comparisons: Python supports chained comparisons like 10 <= x <= 50, which evaluates cleanly as (10 <= x) and (x <= 50).
• Walrus Operator (:=): Python 3.8+ introduced assignment expressions if (n := len(data)) > 10: to assign and evaluate in a single statement.

Self-Check Challenge

Write a function is_bit_set(number: int, bit_position: int) -> bool using the bitwise AND (&) and left shift (<<) operators.