Question One [4 Marks]

Assuming the assignments i = 1, f = 2.0, s = "3" and t = "b4" have been made, evaluate the following code snippets:

(a) i + f

3.0

(b) str(i) + s

"13"

(c) int(f) + int(s)

5

(d) float(t[-1]) * i

4.0

Question Two [4 Marks]

Assuming the assignment s="internationalization" has been made, evaluate:

(a) s[1]

'n'

(b) s[:6] + s[11:13]

'internal'

(c) s[25]

IndexError: string index out of range

index error - this index does not exist, beyond the length of str

(d) s[-1:-10:-3]

nti, -1 starts, -10 stops, and getting every 3rd character

Question Three [4 Marks]

What is wrong with this code? How can you fix it?

if letter == 'a' or letter == 'e' or letter == 'i' or letter == 'o' or letter == 'u:' OR

if letter in 'aeiou': more elegant way of checking for vowels

Question Four [4 Marks]

Given the assignment mylist = [3, ["green","eggs"], True, "computing"], evaluate the following statements and provide: (a) the value the expression evaluates

to; and (b) the value of mylist after the code statement has been executed. Assume that mylist is reassigned to its original value for each sub-question:

(a) mylist[2]

(b) mylist[1][1][:-1]

(a) 'egg', (b) [3, ["green","eggs"], True, "computing"] – No change

egg slicing to position 1, and position 1 of list, and slicing until position -1

(c) mylist.pop()

(a) 'computing', (b) [3, ['green', 'eggs'], True] – last item of mylist is removed

Question 5 [4 Marks]

Rewrite the following code using a for loop, but preserving the remainder of the original code structure:

items = ['eggs', 'spam', 'moreeggs'] for count in range(0, len(items)):

print("We need to buy {0}!".format(items[count]))

items = ['eggs', 'spam', 'moreeggs'] for count in range(len(items)):

print("We need to buy {0}!".format(items[count]))

Question 6 [12 Marks]

Write a function freq_letter(string) that takes a single argument string (a string) and returns a

2-tuple containing the most common letter in string, and how many times it occurs. In case of a tie, it should return the letter that occurred first in the string. For example:

>>> freq_letter('aardvark') ('a', 3)

>>> freq_letter('wooloomooloo') ('o', 8)

>>> freq_letter('abacuses') ('a', 2)

"""

1. Get frequency of each letter - create dict

2. Get the letter with highest frequency

3. In case of a tie, max letter should be the letter that comes first """""

def freq_letter(string):

frequency_dict = {} #frequencies of letters

letter_positions = {} # for number 3, first occurrence of each letter

#1. Get the frequency of each letter

for i in range(len(string)):

letter = string[i]

if letter not in frequency_dict:

frequency_dict[letter] = 0 # {'h': 0, 'e': 0...}

letter_positions[letter] = i # {'h': 0, 'e': 1...}

frequency_dict[letter] += 1 print("FREQ DICT", frequency_dict) print("LETTER POSITIONS", letter_positions)

#2. Get the letter with the highest frequency

max_freq_count = 0 max_letter = ' '

fl_first_position = 0 #position of highest freq letter

for letter in frequency_dict:

if frequency_dict[letter] > max_freq_count: max_freq_count = frequency_dict[letter] max_letter = letter

fl_first_position = letter_positions[letter]

#3 In case of a tie, max letter should be the letter that comes first

elif frequency_dict[letter] == max_freq_count and letter_positions[letter] < fl_first_position: max_letter = letter

fl_first_position = letter_positions[letter]

return (max_letter, max_freq_count) print(freq_letter('hellooooo'))

Question 7 [12 Marks]

Write a function letter_overlap(s1, s2) that takes two string arguments (s1 and s2), and returns the number of unique letters that are present in both strings.

def letter_overlap(s1, s2):

print(set(s1)) print(set(s2))

return len(set(s1) & set(s2))

print(letter_overlap("heya", hey there"))

# Intersection &

# Union |

# Sets {1, 2, 3}

def letter_overlap(s1, s2):

print(set(s1)) print(set(s2))

return set(s1) | set(s2)

print(letter_overlap("heya", hey there"))

def letter_overlap(s1, s2):

print(set(s1)) print(set(s2))

return set(s1) - set(s2)

letter_overlap("heya", hey there")

Question 8 [4 Marks]

What is the output of the following code:

# max (numlist)

#10 - max number

#10 - max of list

-2 - min of list

NameError: avg is not defined

to calculate avg = we can use mean, need to import library for eg.

from statistics import mean extremum(lst, comp = mean))

Identify 3 errors in the following code, determine for each whether it is a syntax, run-time or logic error, and provide a replacement line which corrects the error.

use _ instead of hyphens

Logical error , instead of n we can use total

total = 0

greater_n = 0

total should be backspaced one indentation to be in line with if

syntax error, no indentation