Description

Exercise 1: Operations on a Line of Text via String Manipulation
AIM:
Write a Python program that prompts the user for one line of text without punctuation marks and then asks the user to choose one of the following operations to be done on the line of text:
(a) printing the line of text with all its blank spaces removed,
(b) printing the line of text with each word in reversed order,
(c) printing the number of words in the line of text, by using string manipulation. Your program should check if the user input of the choice of operation is valid. You can assume that the entered line of text has no punctuation marks. Here are the sample input and output of this program:
Enter a line of text without punctuation mark:
I am very very happy
Type a number 1 to 3 to do one of the following operations
1 – print the line of text with all its blank spaces removed
2 – print the line of text with each word in reversed order
3 – print the number of words in the line of text
Enter your choice (1-3): 1
The line of text with all its blank spaces removed:
Iamveryveryhappy
Enter a line of text without punctuation mark:
I am very very happy
Type a number 1 to 3 to do one of the following operations
1 – print the line of text with all its blank spaces removed
2 – print the line of text with each word in reversed order
3 – print the number of words in the line of text Enter your choice (1-3): 2
The line of text with each word in reversed order:
I ma yrev yrev yppah
Enter a line of text without punctuation mark:
I am very very happy
Type a number 1 to 3 to do one of the following operations
1 – print the line of text with all its blank spaces removed
2 – print the line of text with each word in reversed order
3 – print the number of words in the line of text
Enter your choice (1-3): 3
The number of words in the line of text: 5
Enter a line of text without punctuation mark:
I am very very happy
Type a number 1 to 3 to do one of the following operations
1 – print the line of text with all its blank spaces removed
2 – print the line of text with each word in reversed order
3 – print the number of words in the line of text
Enter your choice (1-3): 5
Invalid input. You must type 1 or 2 or 3!
ALGORITHM:
1. Start
2. Input a line of text without punctuation mark
3. Ask the user to choose one of the following operations to be done on the line of text:
(a) Printing the line of text with all its blank spaces removed (by using the string methods split and join)
(b) Printing the line of text with each word in reversed order (by using the string method split to obtain a list of strings composed of each word in the text and then using the slice operator : to slice each string in this list properly)
(c) Printing the number of words in the line of text (by using the string method split to obtain a list of strings composed of each word in the text and then counting the number of elements in this list)
If the user choice of operation is valid, then perform the chosen operation.
4. Output the result of the operation if the user choice of operation is valid; otherwise output an error message
5. End
(The program is shown on the next page.)

PROGRAM:
# Exercise 1: Operations on a Line of Text via String Manipulation
# Written by F K Chow, HKU

# Input a line of text without punctuation mark
string = input(‘Enter a line of text without punctuation mark: ‘)
# Ask the user to choose the operation to be done on the line of text # and perform the chosen operation only if the user choice is valid print(‘Type a number 1 to 3 to do one of the following operations’) print(‘ 1 – print the line of text with all its blank spaces removed’) print(‘ 2 – print the line of text with each word in reversed order’) print(‘ 3 – print the number of words in the line of text’) choice = int(input(‘Enter your choice (1-3): ‘)) if choice == 1:
output = ‘The line of text with all its blank spaces removed: ‘ output += “”.join(string.split(” “)) elif choice == 2:
output = ‘The line of text with each word in reversed order: ‘ stringsp = string.split(” “) output += stringsp[0][::-1] for words in stringsp[1:]: output += ‘ ‘ output += words[::-1] elif choice == 3:
output = ‘The number of words in the line of text: ‘ stringsp = string.split(” “) count = 0 for words in stringsp: if words != ”: count += 1 output += str(count) else:
output = ‘Invalid input. You must type 1 or 2 or 3!’

# Output the result of the operation if the user choice of operation is
# valid; otherwise output an error message print(output)
OUTPUT:

Exercise 2: Caesar Cipher
AIM:
A Caesar cipher is a simple substitution cipher that produces a cipher text by shifting each plain-text letter in a message a fixed number of places down the alphabet in a circular fashion so that the next character after “z” and “Z” are “a” and ”A”, respectively. The plain text is your original message while the cipher text is the encrypted message. For example, if the key value (i.e. the shift length) is
Write a Python program that prompts for a key value in the closed interval [1, 25] and the plain text to encode from the user and then outputs the cipher text as well as the decrypted cipher text. You can assume that the input plain text consists only of letters and spaces. And your program should ask the user to input the key value again if the input value is invalid. If your program is correct, then the decrypted cipher text should match the original plain text.
(Hint: Construct two strings where one contains all the plain-text letters and one contains all the corresponding cipher-text letters. Notice that the letter to substitute is at the same index in both strings.)
ALGORITHM:
1. Start
2. Input a key value and a plain text; ask the user to input again if the input key value is invalid
3. Construct the strings for the plain text and cipher text letters
4. Encode the plain text by substituting each letter with the corresponding cipher text letter and then output the result
5. Decode the cipher text by substituting each letter with the corresponding plain text letter and then output the result
6. End
PROGRAM:
# Exercise 2: Caesar Cipher
# Written by F K Chow, HKU

# Input a key value and a plain text. Ask the user to input again if
# the input key value is invalid
while True:
n = int(input(‘Enter a key value n (1-25): ‘)) if n > 0 and n < 26:
break
print(‘Invalid input! n must be an integer in the range of 1-25!’) string = str(input(‘Enter a plain text: ‘))

# Construct the strings for the plain text and cipher text letters plaintxtlett = ‘abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ’ ciphertxtlett = plaintxtlett[n:26] ciphertxtlett += plaintxtlett[0:n] ciphertxtlett += plaintxtlett[n+26:52] ciphertxtlett += plaintxtlett[26:n+26]

# Encode the plain text and output the result cipher_text = ” for ch in string: if ch != ‘ ‘:
index = plaintxtlett.index(ch) cipher_text += ciphertxtlett[index] else:
cipher_text += ‘ ‘
print(‘The cipher text is’, cipher_text)

# Decode the plain text and output the result decryp_text=” for ch in cipher_text: if ch != ‘ ‘:
index = ciphertxtlett.index(ch) decryp_text += plaintxtlett[index] else:
decryp_text += ‘ ‘
print(‘The decrypted cipher text is’, decryp_text)
(The output is shown on the next page.)
OUTPUT:

Exercise 3: Vector Manipulation
AIM:
Write a Python program that prompts the user for two vectors of the same length, computes their sum, difference, and dot product by manipulating the lists storing these vectors, and finally outputs the results. You can assume that each vector is input as a comma-space-separated list of integers enclosed by square brackets. And your program should ask the user to input the vectors again if they have different length. Here are the sample input and output of this program:
Enter the vector A: [2, 4, 6, 8]
Enter the vector B: [1, 2, 3]
Invalid input! Vectors A and B must have the same length.
Enter the vector A: [2, 4, 6, 8] Enter the vector B: [1, 2, 3, 4]
A+B = [3, 6, 9, 12]
A-B = [1, 2, 3, 4]
A.B = 60
ALGORITHM:
1. Start
2. Input two vectors and store them as lists of integers using string methods strip and split. Check whether the vectors have the same length by comparing the lengths of the lists. Ask user to input the vectors again if they have different lengths.
3. Compute the sum, difference, and dot product of these two vectors by manipulating the lists storing them via list comprehension
4. Output the results of the computation in step 3
5. End
PROGRAM:
# Exercise 3: Vector Manipulation
# Written by F K Chow, HKU

# Input two vectors of the same length and store them as lists while True:
strA = input(‘Enter the vector A: ‘) strB = input(‘Enter the vector B: ‘) strA = strA.strip(‘[]’) strB = strB.strip(‘[]’) lstA = strA.split(‘, ‘) lstB = strB.split(‘, ‘) if len(lstA) == len(lstB):
A = [int(i) for i in lstA] B = [int(i) for i in lstB] break
print(‘Invalid input! Vectors A and B must have the same length.’)

# Compute the sum, difference, and dot product of these two vectors by
# manipulating the lists storing them
AplusB = [A[i]+B[i] for i in range(len(A))]
AminusB = [A[i]-B[i] for i in range(len(A))]
AdotB = sum([A[i]*B[i] for i in range(len(A))])

# Output the results print(‘A+B =’, AplusB) print(‘A-B =’, AminusB) print(‘A.B =’, AdotB)
OUTPUT:

Exercise 4: Bubble Sort
AIM:
Bubble sort is a simple algorithm that sorts a collection of data by ‘bubbling’ values to the end of the list over successive passes like air bubbles rising in water. Here are the procedures for sorting a list of numbers in ascending order using bubble sort:
(a) Starting from the first element, compare each adjacent pair of elements of the list in turn and swap the elements if the former element has a larger value. After all the elements in the list have been compared, the largest element will be at the end of the list. This completes the first pass of the algorithm.
(b) Repeat the process in (a) from the first to the second last element of the list. At the end of the second pass, the second largest element will be at the second last position of the list.
(c) Repeat the process in (a) again in a similar manner as in (b) until no more swapping occurs in a pass.
Write a Python program that generates a list composed of 10 random integers in the range of 1 to 100, prints out the list, and finally uses bubble sort to sort the integers in the list in ascending order with the updated list printed out after each swapping. Here is the sample output of this program:
Sorting Process of a List of Integers by Bubble Sort:
[83, 74, 89, 26, 18, 69, 75, 98, 47, 77]
[74, 83, 89, 26, 18, 69, 75, 98, 47, 77]
[74, 83, 26, 89, 18, 69, 75, 98, 47, 77]
[74, 83, 26, 18, 89, 69, 75, 98, 47, 77]
[74, 83, 26, 18, 69, 89, 75, 98, 47, 77]
[74, 83, 26, 18, 69, 75, 89, 98, 47, 77]
[74, 83, 26, 18, 69, 75, 89, 47, 98, 77]
[74, 83, 26, 18, 69, 75, 89, 47, 77, 98]
[74, 26, 83, 18, 69, 75, 89, 47, 77, 98]
[74, 26, 18, 83, 69, 75, 89, 47, 77, 98]
[74, 26, 18, 69, 83, 75, 89, 47, 77, 98]
[74, 26, 18, 69, 75, 83, 89, 47, 77, 98]
[74, 26, 18, 69, 75, 83, 47, 89, 77, 98]
[74, 26, 18, 69, 75, 83, 47, 77, 89, 98]
[26, 74, 18, 69, 75, 83, 47, 77, 89, 98]
[26, 18, 74, 69, 75, 83, 47, 77, 89, 98]
[26, 18, 69, 74, 75, 83, 47, 77, 89, 98]
[26, 18, 69, 74, 75, 47, 83, 77, 89, 98]
[26, 18, 69, 74, 75, 47, 77, 83, 89, 98]
[18, 26, 69, 74, 75, 47, 77, 83, 89, 98]
[18, 26, 69, 74, 47, 75, 77, 83, 89, 98]
[18, 26, 69, 47, 74, 75, 77, 83, 89, 98] [18, 26, 47, 69, 74, 75, 77, 83, 89, 98] ALGORITHM:
1. Start
2. Import the randint function from the random module
3. Generate a list of 10 random integers in the range of 1 to 100 and print out the list
4. Use bubble sort to sort the integers in the list in ascending order by doing the followings for i = 1 to 10:
(a) Compare each adjacent pair of elements of the list from the first element to the ith last element in turn. For each comparison, if the former element has a larger value, swap the two elements and then output the updated list.
(b) If no swapping occurs in (a), then jump to step 5.
5. End
PROGRAM:
# Exercise 4: Bubble Sort
# Written by F K Chow, HKU

# Import the randint function from the random module from random import randint

# Generate a list of 10 random integers in the range of 1 to 100 and
# print out the list
list = [randint(1, 100) for i in range(10)]
print(“Sorting Process of a List of Integers by Bubble Sort:”) print(list)

# Use bubble sort to sort the integers in the list in ascending order
# with the updated list printed out after each swapping for i in range(1, 10): noswapping = True for j in range(10-i): if list[j] > list[j+1]: temp = list[j] list[j] = list[j+1] list[j+1] = temp print(list) noswapping = False if noswapping:
break
OUTPUT:

Exercise 5: Printing a Histogram
AIM:
District Numbers of Students (nearest hundreds) District Numbers of Students (nearest hundreds)
Central & Western 7 Sai Kung 7
Wan Chai 25 Sha Tin 8
Eastern 22 Tai Po 8
Southern 8 North 8
Yau Tsim Mong 14 Yuen Long 27
Sham Shui Po 22 Tuen Mun 7
Kowloon City 29 Tsuen Wan 18
Wong Tai Sin 6 Kwai Tsing 0
Kwun Tong 15 Islands 0
Write a Python program to show the statistics of the data in this table by printing a histogram in the following format:
(in nearest hundreds)
Central & Western | ******* (7)
Wan Chai | ************************* (25)

Islands | (0)
Your program should define some variables to store the given data and then print the variables using print with the format specifier.
ALGORITHM:
1. Start
2. Define two lists to store the district names and the number of students in each district
3. Print a histogram to show the statistics of the given data by using print with the format specifier
4. End
PROGRAM:
# Exercise 5: Printing a Histogram
# Written by F K Chow, HKU

# Define two lists to store the district names and the number of
# students in each district
district = [‘Central & Western’, ‘Wan Chai’, ‘Eastern’, ‘Southern’,
‘Yau Tsim Mong’, ‘Sham Shui Po’, ‘ Kowloon City’,
‘Wong Tai Sin’, ‘Kwun Tong’, ‘Sai Kung’, ‘Sha Tin’,
‘Tai Po’, ‘ North’, ‘Yuen Long’, ‘Tuen Mun’, ‘Tsuen Wan’,
‘Kwai Tsing’, ‘Island’]
studentnum = [7, 25, 22, 8, 14, 22, 29, 6, 15, 7, 8, 8, 8, 27, 7, 18, 0, 0]

print(‘(in nearest hundreds)’) for i in range(len(district)):
print(‘{:>17s} | ‘.format(district[i]), end=”) if studentnum[i] != 0:
print(‘{:s} ({:d})’.format(‘*’*studentnum[i], studentnum[i])) else:
print(‘(0)’)
(The output is shown on the next page.)

OUTPUT: