Track 5 · Lesson 10 of 12

Pure functions and side effects

Write predictable functions that depend only on their arguments, avoid surprising changes to the caller's lists, and check functions with assert.

You will be able to

• Define a pure function and name the common kinds of side effect
• Explain why changing a list argument inside a function also changes the caller's list
• Return a new list instead of modifying the one passed in
• Check a function's behaviour with assert statements