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Python if...else Statement

Conditional statements execute code blocks based on boolean conditions. Python uses if, elif (else if), and else with indentation to define blocks.

if / elif / else

score = 85

if score >= 90:
    grade = "A"
elif score >= 80:
    grade = "B"
elif score >= 70:
    grade = "C"
else:
    grade = "F"

print(f"Score: {score}, Grade: {grade}")  # Score: 85, Grade: B

Ternary (Conditional Expression)

# value_if_true if condition else value_if_false
age = 20
status = "adult" if age >= 18 else "minor"
print(status)  # adult

# Practical: safe division
b = 0
result = a / b if b != 0 else 0

Nested and Combined Conditions

# Combined with logical operators
age = 25
has_id = True

if age >= 18 and has_id:
    print("Access granted")
elif age >= 18 and not has_id:
    print("Show your ID")
else:
    print("Too young")

# Checking None / empty values
name = None
if name:
    print(f"Hello, {name}")
else:
    print("Hello, Guest")  # This runs (None is falsy)

match Statement (Python 3.10+)

# Structural pattern matching
command = "quit"
match command:
    case "start":
        print("Starting...")
    case "stop":
        print("Stopping...")
    case "quit" | "exit":
        print("Goodbye!")
    case _:
        print(f"Unknown: {command}")

• Python uses indentation (4 spaces) to define blocks — no curly braces.
• Falsy values: 0, "", [], {}, None, False.
• Use match (3.10+) for clean multi-way branching on values or patterns.