Nested Lists: Flatten, Search, and Why Loops Fall Short

Why does 3 in [[1, 2, 3]] return False, and how does recursion flatten and search nested lists whose depth you can't know in advance?

Finger exercises

Short drills on what this video just taught. Write the code, run the checks, and reveal the answer only if you are stuck.

0 / 5 passed

Exercise 1 of 5

The membership paradox

The in operator only ever looks at the top-level elements of the list you hand it.

Two lists are given: flat = [10, 20, 30] and nested = [[10, 20, 30]]. Assign to membership a list of exactly three booleans, in this order:

whether 20 is an element of flat
whether 20 is an element of nested
whether 20 is an element of the single inner list that nested holds

Write each entry as a test that Python evaluates for you — do not type True / False out by hand.

# Exercise 1: three membership tests — two asked at the top level, one asked a level down.
flat = [10, 20, 30]
nested = [[10, 20, 30]]

membership = ...  # your code here — a list of three booleans

# Exercise 1: three membership tests — two asked at the top level, one asked a level down.
flat = [10, 20, 30]
nested = [[10, 20, 30]]

membership = ...  # your code here — a list of three booleans

Python runs in your browser

⌘/Ctrl + Enter runs

is a list

has one entry per question

every entry is a boolean

gets both top-level questions right

gets the question asked one level down right

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