Control Flow: Conditionals

Control flow refers to the order in which individual statements, instructions, or function calls are executed. The most common way to branch the flow of execution is using Conditional Statements.

1. If, Elif, and Else

Python uses if, elif (else if), and else to execute different blocks of code based on logical conditions.

score = 85

if score >= 90:
    print("Grade: A")
elif score >= 80:
    print("Grade: B")
else:
    print("Grade: C")

Indentation: Unlike languages that use curly braces {} (C++, Java, JS), Python uses whitespace indentation to define the scope of a block. This is enforced by the compiler and is central to Python's design philosophy.

2. Truthiness and Falsiness

In Python, every object has an inherent Boolean value. This concept is called Truthiness.

Falsy Values	Everything Else (Truthy)
`None`	Any non-zero number
`False`	Non-empty strings (`"Hello"`)
`0` (and `0.0`)	Non-empty lists, dicts, sets
`""` (Empty string)
`[]`, `{}`, `set()` (Empty collections)

name = ""
if not name:
    print("Name is empty") # This will execute because "" is Falsy

3. Structural Pattern Matching (Match-Case)

Introduced in Python 3.10, the match statement is a powerful way to branch logic based on the structure of data—similar to switch-case in other languages but significantly more capable.

status = 404

match status:
    case 200:
        print("Success")
    case 404:
        print("Not Found")
    case 500 | 501: # OR operator in cases
        print("Server Error")
    case _:
        print("Unknown Status") # Default catch-all

Interview Pro-Tips: The Ternary Operator

Python supports conditional expressions (often called the ternary operator) for simple one-line branches.

# Result = <Value if True> if <Condition> else <Value if False>
access_allowed = True if age >= 18 else False

While efficient, be careful not to nest these too deeply, as it violates the principle of Readability (The Zen of Python).