Control Flow Truthy and Falsy

Learning objective: By the end of this lesson, students will understand the concept of truthy and falsy values in JavaScript.

Truthy and falsy in Python

Like JavaScript, every piece of data in Python is considered either truthy or falsy.

Conditional expressions used to construct branching and looping code rely on an expression evaluating to True/truthy or False/falsy to determine which path the code will follow.

Just like in JavaScript, most things in Python are considered to be truthy, so it’s easier to remember what is falsy instead.

Here’s what’s falsy in Python:

• False
• None
• Zero in any numeric type: 0 0.0
• Empty sequences or collections:
  • '' (empty string)
  • [] (empty list)
  • () (empty tuple)
  • {} (empty dictionary)
  • range(0) (empty range)

🧠 The first thing you might notice here is how closely this aligns with what is falsy in JavaScript. Note that [] and {} in JavaScript are truthy, but falsy in Python.