Question

Problem 1

This program is about dictionaries. We want to use a dictionary to store frequency count of each letter in a string. Write a Python program to do the following:

(a) Ask the user to enter a string. Convert all letters to uppercase. Count the frequency of each letter in the string. Store the frequency counts in a dictionary. You should count letters only. Do not count any other characters such as digits and space. Display the dictionary.

(b) Ask the user to enter a letter. Convert it to uppercase. Check whether the letter is in the dictionary. If it is not, display the message “Letter not in dictionary”. Otherwise, display the frequency count of that letter, remove the letter from the dictionary and display the dictionary after that letter has been removed.

(c) Create a list to store the letters that are in the dictionary. Sort and display the list.

The following is an example.

Enter a string: Magee, Mississippi

Dictionary: {'M': 2, 'A': 1, 'G': 1, 'E': 2, 'I': 4, 'S': 4, 'P': 2}

Choose a letter: s

Frequency count of that letter: 4

Dictionary after that letter removed: {'M': 2, 'A': 1, 'G': 1, 'E': 2, 'I': 4, 'P': 2}

Letters sorted: ['A', 'E', 'G', 'I', 'M', 'P']

Answer 1

Program:

# asking user for string
user_string = input("Enter a string: ")

# converting to uppercase
user_string = user_string.upper()

# creating empty dictionary
freq = {}

# iterate through each character in string
for i in user_string:
    # checking if selected character is alphabet or not
    if i.isalpha():
        # checking if it is in dictionary
        if i in freq:
            # incrementing the count by 1
            freq[i] += 1
        else:
            # creating a new entry in dictionary with initial count as 1
            freq[i] = 1

# printing dictionary
print("Dictionary: ", freq)

# asking user to enter a letter
letter = input("Choose a letter: ")

# converting the letter to upper case
letter = letter.upper()

# checking if letter is in dictionary
if letter in freq:
    # printing count of that letter
    print("Frequency count of that letter: ", freq[letter])
    
    # removing the letter from dictionary
    freq.pop(letter)
    
    # printing dictionary after removing the letter
    print("Dictionary after that letter removed: ", freq)
else:
    print("Letter not in dictionary")

# creating a list with all the dictionary keys
letter_list = list(freq.keys())

# sorting the list
letter_list.sort()

# printing sorted list
print(letter_list)

Output:

Enter a string: Magee, Mississippi
Dictionary: {'M': 2, 'A': 1, 'G': 1, 'E': 2, 'I': 4, 'S': 4, 'P': 2}
Choose a letter: s
Frequency count of that letter: 4
Dictionary after that letter removed: {'M': 2, 'A': 1, 'G': 1, 'E': 2, 'I': 4, 'P': 2}
['A', 'E', 'G', 'I', 'M', 'P']

Screenshots: