Hackerrank Regular Expressions (re module)

Question 1

Which re function returns a match object only if the pattern matches at the BEGINNING of the string?

Accepted Answer

re.match()

Answer

re.search()

Answer

re.fullmatch()

Answer

re.findall()

Question 2

What does re.findall(r'\d+', 'abc123def456') return?

Accepted Answer

['123', '456']

Answer

['1', '2', '3', '4', '5', '6']

Answer

[123, 456]

Answer

'123'

Question 3

What is the output of the following?

python
import re
m = re.search(r'(\w+)@(\w+)', 'user@domain.com')
print(m.group(1))

Accepted Answer

user

Answer

user@domain

Answer

domain

Answer

user@domain.com

Question 4

What does re.sub(r'\s+', '-', 'hello   world	there') return?

Accepted Answer

'hello-world-there'

Answer

'hello   world	there'

Answer

'hello-world	there'

Answer

'hello - world - there'

Question 5

Which pattern correctly matches a string that starts with a digit and ends with a letter (case-insensitive)?

Accepted Answer

r'^\d.*[a-zA-Z]$'

Answer

r'\d.*[a-zA-Z]'

Answer

r'^[0-9][a-z]$'

Answer

r'\d+[a-zA-Z]+'

Question 6

What is the purpose of re.compile() compared to using re.match() directly?

Accepted Answer

It pre-compiles the pattern into a reusable regex object, improving performance when the same pattern is used many times

Answer

It validates that the regex pattern is syntactically correct without matching anything

Answer

It converts the pattern to a case-insensitive version automatically

Answer

It is required before any regex function can be called in Python