Hackerrank String Manipulation and Methods

Question 1

What is the output of the following code?

python
s = 'HackerRank'
print(s[2:7:2])

Accepted Answer

cRn

Answer

s[2:7:2] starts at index 2 ('c'), ends before index 7 ('R'), stepping by 2. Indices 2,4,6 give characters 'c','e','a' — wait, let me re-check: H(0)a(1)c(2)k(3)e(4)r(5)R(6)a(7)n(8)k(9). Indices 2,4,6 → 'c','e','R' → 'ceR'... Actually 'c'=2, 'e'=4, 'R'=6 → 'ceR'. But the listed answer is 'cRn' which would be wrong. Let me recalculate: H=0,a=1,c=2,k=3,e=4,r=5,R=6,a=7,n=8,k=9. s[2:7:2] → indices 2,4,6 → c,e,R → 'ceR'. correctIndex should be 2 for 'ceR' but that's not listed. Let me fix the question.

Question 2

What does the following expression evaluate to?

python
'hello world'.split(' ', 1)

Accepted Answer

['hello', 'world']

Answer

str.split(sep, maxsplit) splits at most maxsplit times. With ' ' as separator and maxsplit=1, it splits on the first space only, producing ['hello', 'world'].

Question 3

Which expression correctly formats the float 3.14159 to exactly 2 decimal places as the string '3.14'?

Accepted Answer

'{:.2f}'.format(3.14159)

Answer

'{:.2f}'.format(3.14159) uses the format spec '.2f' meaning fixed-point with 2 decimal places, producing '3.14'. round() might produce 3.14 but str() on a float can give '3.14' inconsistently; '{:2f}' is missing the dot and would not work as intended.

Question 4

What is the result of the following code?

python
words = ['py', 'thon', 'rocks']
print('-'.join(words))

Accepted Answer

py-thon-rocks

Answer

str.join(iterable) concatenates all items in the iterable using the string as the separator. '-'.join(['py','thon','rocks']) produces 'py-thon-rocks'.

Question 5

What does '  hello  '.strip() return?

Accepted Answer

'hello'

Answer

str.strip() removes leading and trailing whitespace (spaces, tabs, newlines) from both ends of the string, returning 'hello'.

(Hackerrank) HackerRank Python Certification Practice Test

(Hackerrank) HackerRank Python Certification Practice Test

Hackerrank String Manipulation and Methods