Truthiness, When Non-Booleans Act Like Booleans

Both languages let you use non-Boolean values where a Boolean is expected. Each value is then judged truthy or falsy.

The falsy values are almost identical in both languages: 0, empty string "", None/null, False/false, and empty collections in Python. Everything else is truthy.

Truthiness

PYTHON

print(bool(0))        # False
print(bool(""))       # False
print(bool([]))       # False, empty list
print(bool("Sankofa"))# True
print(bool(42))       # True

JAVASCRIPT

console.log(Boolean(0));         // false
console.log(Boolean(""));        // false
console.log(Boolean([]));        // TRUE, surprise!
console.log(Boolean("Sankofa")); // true
console.log(Boolean(42));        // true

Compare → Nearly identical, with one real trap. An empty list is FALSY in Python but an empty array is TRUTHY in JavaScript. This is a genuine language difference that catches experienced developers. In JavaScript, check arr.length === 0 instead.

EXAMPLE

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YOUR TURN

Your turn → This is the default-value pattern, used constantly in real code. Set name to your own name and rerun, the backup disappears.

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Syntax has to be exact. Every quote, bracket and parenthesis needs its partner, and in Python the spaces at the start of a line count. One slip and the program won't run; the message will say where.

✦ Why truthiness earns its complexity

It lets you write display = name or "Friend" instead of a five-line check. Powerful, and exactly why you must know that 0 is falsy. If a user's score is 0, score or 100 quietly hands back 100. Knowing the falsy list is what separates a bug from a feature.

◈ Graded Challenge

Using the applicant variables, create merit (GPA 3.5 or above AND enrolled) and service (100 or more hours OR first generation). Mind your operators.

Name it exactly: merit, service

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