PCAP Comprehensions and Iterators

Question 1

Which syntax creates a list comprehension in Python?

Accepted Answer

[x for x in range(5)]

Answer

List comprehensions use square brackets: `[expression for item in iterable]`.

Question 2

What does a generator expression return compared to a list comprehension?

Accepted Answer

A lazy iterator evaluated on demand

Answer

A generator expression (using parentheses) returns an iterator that yields values lazily, using less memory.

Question 3

What is the result 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 4

How do you add a condition to a list comprehension to include only even numbers?

Accepted Answer

[x for x in range(10) if x%2==0]

Answer

A conditional list comprehension uses `if condition` at the end: `[x for x in iterable if condition]`.

Question 5

Which syntax creates a dictionary comprehension?

Accepted Answer

{k:v for k,v in items}

Answer

Dictionary comprehensions use `{key: value for ...}` syntax with curly braces and a colon.

PCAP - Certified Associate in Python Programming Practice Test