Peer Instruction: Strings Multiple Choice Questions¶

11-9-1: What does the following code print?

game = 'Lost Vikings'
print(game[5:-1])

kings
Try again. s[i:j] extracts characters beginning at s[i] and ending about not including s[j]. And the first index in a string is index 0.
king
Try again. s[i:j] extracts characters beginning at s[i] and ending about not including s[j]. And the first index in a string is index 0. Index -1 is the right 1 character.
Viking
Correct! s[i:j] extracts characters beginning at s[i] and ending about not including s[j].
Vikings
Try again. s[i:j] extracts characters beginning at s[i] and ending about not including s[j]. Index -1 is the right 1 character. So 's' is not included.
ikings
Try again. s[i:j] extracts characters beginning at s[i] and ending about not including s[j]. And the first index in a string is index 0.

11-9-2: What does the following code print?

game = 'Lost Vikings'
print(game[2:-6])

st V
Correct! s[i:j] extracts characters beginning at s[i] and ending about not including s[j]. s[2] is the third character from left, and s[-6] is the sixth character from right. s[2] = 's' and s[-6] = 'i'.
ost V
Try again. s[i:j] extracts characters beginning at s[i] and ending about not including s[j]. s[2] is the third character from left. s[2] = 's'.
iking
Try again. s[i:j] extracts characters beginning at s[i] and ending about not including s[j]. s[2] is the third character from left, and s[6] is the sixth character from right. s[2] = 's' and s[-6] = 'i'.
st Vi
Try again. s[i:j] extracts characters beginning at s[i] and ending about not including s[j]. s[-6] is the sixth character from right. s[-6] = 'i'.
Viking
Try again. s[i:j] extracts characters beginning at s[i] and ending about not including s[j]. s[2] is the third character from left, and s[-6] is the sixth character from right. s[2] = 's' and s[-6] = 'i'.

11-9-3: What does the following code print?

game = 'Lost Vikings'
print(game[-6:-1])

ost Vikings
Try again. s[i:j] extracts characters beginning at s[i] and ending about not including s[j]. s[-6] is the sixth character from right, and s[-1] is the first character from right. There is no index 0 when counting from right to left.
ost Viking
Try again. s[i:j] extracts characters beginning at s[i] and ending about not including s[j]. s[-6] is the sixth character from right, and s[-1] is the first character from right. There is no index 0 when counting from right to left.
ikings
Try again. s[i:j] extracts characters beginning at s[i] and ending about not including s[j]. s[-1] is the first character from right. There is no index 0 when counting from right to left.
iking
Correct! s[i:j] extracts characters beginning at s[i] and ending about not including s[j]. We can use negative indices in the slice syntax as well.
Vikings
Try again. s[i:j] extracts characters beginning at s[i] and ending about not including s[j]. s[-1] is the first character from right. There is no index 0 when counting from right to left.

11-9-4: What does the following code print?

s = 'Mississauga'
t = len(s.replace('ss', 'a'))
print(t)

11
Try again. s.replace(old, new): return s but with all occurrences of old replaced by new. The new s = 'Miaiaauga'. And the length of new s is 9.
ss
Try again. t is the length of the new string because it equals to len(s).
10
Try again. s.replace(old, new): return s but with all occurrences of old replaced by new. The new s = 'Miaiaauga'. And the length of new s is 9.
Miaaiaaauga'
Try again. t is the length of the new string because it equals to len(s).
None of the above
Correct! s.replace(old, new): return s but with all occurrences of old replaced by new. The new s = 'Miaiaauga'. And the length of new s is 9.

11-9-5: What string is produced by the following code?

'cave'.center(8, 'x')

'xxcavexx'
Correct! In string.center(length, character), the length is the length of the returned string and the character to fill the missing space on each side.
' cave '
Try again. In string.center(length, character), the character to fill the missing space on each side. Here the character is 'x'.
'xxxxcavexxxx'
Try again. In string.center(length, character), the length is the length of the returned string. The length here should be 8 rather than 12.
' cave '
Try again. In string.center(length, character), the length is the length of the returned string and the character to fill the missing space on each side. The length here should be 8 rather than 12 and the filling character is 'x'.

11-9-6: What is the value of mystery?

ch = 'w'
val = ord('a') + 6 - (ord('z') - ord(ch) + 1)
mystery = chr(val)

'a'
Try again. ord converts characters to codes and chr converts codes to characters. ord('a') = 97, ord('z') = 122, ord(ch) = 119, val = 99. Therefore, mystery = 'c'.
'b'
Try again. ord converts characters to codes and chr converts codes to characters. ord('a') = 97, ord('z') = 122, ord(ch) = 119, val = 99. Therefore, mystery = 'c'.
'c'
Correct! ord converts characters to codes and chr converts codes to characters. ord('a') = 97, ord('z') = 122, ord(ch) = 119, val = 99. Therefore, mystery = 'c'.
'd'
Try again. ord converts characters to codes and chr converts codes to characters. ord('a') = 97, ord('z') = 122, ord(ch) = 119, val = 99. Therefore, mystery = 'c'.
'e'
Try again. ord converts characters to codes and chr converts codes to characters. ord('a') = 97, ord('z') = 122, ord(ch) = 119, val = 99. Therefore, mystery = 'c'.

11-9-7: What is the value of mystery?

ch = 'x'
val = ord('a') + 4 - (ord('z') - ord(ch) + 1)
mystery = chr(val)

'a'
Try again. ord converts characters to codes and chr converts codes to characters. ord('a') = 97, ord('z') = 122, ord(ch) = 128, val = 98. Therefore, mystery = 'b'.
'b'
Correct! ord converts characters to codes and chr converts codes to characters. ord('a') = 97, ord('z') = 122, ord(ch) = 128, val = 98. Therefore, mystery = 'b'.
'c'
Try again. ord converts characters to codes and chr converts codes to characters. ord('a') = 97, ord('z') = 122, ord(ch) = 128, val = 98. Therefore, mystery = 'b'
'd'
Try again. ord converts characters to codes and chr converts codes to characters. ord('a') = 97, ord('z') = 122, ord(ch) = 128, val = 98. Therefore, mystery = 'b'
'e'
Try again. ord converts characters to codes and chr converts codes to characters. ord('a') = 97, ord('z') = 122, ord(ch) = 128, val = 98. Therefore, mystery = 'b'

11-9-8: What does the following code print?

s1 = '0'
s2 = 'a{' + s1 + '}b'
print(s2.format(4))

a{0}b
Try again. The format(4) method formats the specified value(4) and insert them inside the string's placeholder. The placeholder is defined using curly brackets: {}.
ab
Try again. s2 = a{0}b. The format(4) method formats the specified value(4) and insert them inside the string's placeholder. The placeholder is defined using curly brackets: {}.
a4b
Correct! The format(4) method formats the specified value(4) and insert them inside the string's placeholder.
The code does not run
Try again. The code can run. {n} inserts the argument, thereefore s2 = a{0}b. The format(4) method formats the specified value(4) and insert them inside the string's placeholder. The placeholder is defined using curly brackets: {}.

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