map() function in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the map() function do in Python?

The map() function applies a given function to each item of an iterable (like a list) and returns a map object with the results.

beginner

How do you convert the result of map() into a list?

You can convert the map object to a list by using the list() function, like list(map(function, iterable)).

intermediate

Can map() work with multiple iterables? If yes, how?

Yes, map() can take multiple iterables. The function you provide must accept as many arguments as there are iterables. It applies the function to items from all iterables in parallel.

beginner

What type of object does map() return?

map() returns a map object, which is an iterator that generates the results on demand.

intermediate

Why is map() useful compared to a for-loop?

map() is useful because it can make code shorter and clearer by applying a function to all items without writing an explicit loop. It also can be more memory efficient since it returns an iterator.

What does map(str, [1, 2, 3]) return?

A An error because str is not a list

B A list of strings ['1', '2', '3']

C A string '123'

D An iterator that converts each number to a string

map() returns an iterator, not a list. You can convert it to a list with list().

How do you apply a function to two lists element-wise using map()?

A Use a for-loop only

B Use <code>map(function(list1, list2))</code>

C Use <code>map(function, list1, list2)</code>

D Use <code>map(function, [list1, list2])</code>

You pass the function and both lists as separate arguments to map().

What happens if the iterables passed to map() have different lengths?

A The function continues until the longest iterable is exhausted

B The function stops when the shortest iterable is exhausted

C An error is raised

D The shorter iterable is repeated

map() stops when the shortest iterable runs out of items.

Which of these is a correct way to get a list of squares from [1, 2, 3] using map()?

A list(map(lambda x: x**2, [1, 2, 3]))

B map(lambda x: x**2, [1, 2, 3])

C list(map([1, 2, 3], lambda x: x**2))

D map([1, 2, 3]**2)

You must pass the function first, then the iterable, and convert the map object to a list.

Is the following statement true or false?
"map() immediately applies the function to all items and stores the results in memory."

A False

B True

C Only if the iterable is a list

D Only if the function is built-in

map() returns an iterator that applies the function lazily, not storing all results at once.

Explain how the map() function works and give a simple example.

Think about how you can change each item in a list without a loop.

Describe how you can use map() with multiple lists and what happens if they have different lengths.

Imagine pairing items from two lists and applying a function to each pair.