Python Python List Comprehensions and Generators

Question 1

What is the output of `[x**2 for x in range(4)]`?

Accepted Answer

[0, 1, 4, 9]

Answer

range(4) produces 0, 1, 2, 3, and squaring each gives [0, 1, 4, 9].

Question 2

Which syntax creates a generator expression in Python?

Accepted Answer

(x for x in range(10))

Answer

Parentheses around a comprehension-style expression create a generator, not a list.

Question 3

What does the `yield` keyword do in a Python function?

Accepted Answer

Pauses execution and returns a value to the caller, resuming on next call

Answer

yield turns a function into a generator, pausing at each yield and resuming from that point when next() is called.

Question 4

What is the output of `list(x for x in range(5) if x % 2 == 0)`?

Accepted Answer

[0, 2, 4]

Answer

The condition x % 2 == 0 filters to even numbers 0, 2, and 4 from range(5).

Question 5

Which of the following creates a set comprehension?

Accepted Answer

{x*2 for x in range(5)}

Answer

Curly braces with a single expression and no colon create a set comprehension.

Python Practice Test