None

Python's single value for "no value", what a function gives back when it returns nothing, and what you test with is None.

Depth 1 · Foundation

You know where None comes from (a function with no return, methods like sort, a missing dictionary key with get), test for it with is None, and choose between returning None and raising an exception.

Depths of understanding

1
Foundation
You know where None comes from (a function with no return, methods like sort, a missing dictionary key with get), test for it with is None, and choose between returning None and raising an exception.
Opens after
Return valuesNone is what comes back from a function that doesn't return a value.ExceptionsReturning None and raising an exception are the two ways a function can say it has no answer; choosing needs both.

Your path here

What's still between you and None, depth 1, in the order you can learn it.

Where it fits

Builds on

Return valuesFunctions ExceptionsWriting Correct Code

This concept

NoneData Types

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Type annotationsWriting Correct Code

Builds onThis conceptOpens upReturn valuesFunctions ExceptionsWriting Correct Code NoneData Types Type annotationsWriting Correct Code