Conditional Statements

if / else and switch statements run code only when a condition is true.

Beginner

A conditional checks a Boolean expression and picks a branch:

temperature = 41
if temperature > 40:
    print("Overheat — fan on")
elif temperature > 30:
    print("Warm")
else:
    print("Normal")

In C, C++ and Java, a switch statement selects among many constant values:

switch (command) {
    case 'F': forward(); break;
    case 'B': backward(); break;
    default:  stop();
}

Forgetting break in C causes fall-through into the next case — sometimes useful, usually a bug.

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