Challenge TC101 Frequency Dictionary

--Originally published at Programming

The first challenge posted by ken is the next one:

Using a file full of words, create a program that counts how many times each word is repeated in the file. We are going to do first some functions that’ll help us throughout this process. First we’ll create a function read_from_file which will basically open a file and read from it every word, storing them in a list. This function returns a list of words.

def read_from_file(file):
    """
    :param file: The file words are going to be read from
    :return: a list with the words inside the file
    """
    lista = []
    try:
        f = open(file, 'r')
        for line in f:
            line = line.strip('\n')  # Get rid of the \n at the end of each line
            lista += line.split(" ")  # get every word of the line and store it inside a list
        f.close()
    except IOError:
        print("Cannot open " + file)
    return lista

Now we are going to create a function that counts the frequencies of the words inside a list by storing it in a dictionary. The dictionary keys will be the words and the values will be the number of times each word appears in the list. This function returns a dictionary with frequencies.

def count_frequency(words):
    """
    :param words: List of words
    :return: A dictionary with frequencies of words
    """
    frequency_words = {}
    for word in words:  # iterate over the list
        # If the word is not already inside the dictionary's keys, create it
        if word not in frequency_words.keys():
            frequency_words[word] = 1
        else:
            frequency_words[word] += 1
    return frequency_words

Now we have the dictionary and it’s time for us to test whether this program works or not. So create a text file with random words, repeat some of them on purpose so that you can check

the program works. For this example I’m creating a text file named words.txt that looks like this:

Now let’s create some test cases so that we can check if this program is working properly:

Test Cases

adult – 5 (The program should map the word adult to 5)
dog – 2 (The program should map the word dog to 2)
ship – 4 (The program should map the word ship to 4)

Now let’s run the program. Below the functions we just created we need to write these lines of code:

 # Create a list of words
words = read_from_file("words.txt") 
# Create a word frequencies based on the words
words_frequency = count_frequency(words)
print(words_frequency)

Now save and run your file. The output should be a dictionary (Remember that dictionaries are data structures and therefore the items inside don’t have any order) that looks like this:

{'sheet': 1, 'ship': 4, 'dog': 2, 'sheep': 1, 'father': 2, 
'cat': 5, 'brother': 3, 'adult': 5, 'step': 2, 'mother': 2, 'airplane': 2}

Now look at your test cases and compare them to your output.

def read_from_file(file): """ :param file: The file words are going to be read from :return: a list with the words inside the file """ lista = [] try: f = open(file, 'r') for line in f: line = line.strip('\n') # Get rid of the \n at the end of each line lista += line.split(" ") # get every word of the line and store it inside a list f.close() except IOError: print("Cannot open " + file) return lista

def count_frequency(words): """ :param words: List of words :return: A dictionary with frequencies of words """ frequency_words = {} for word in words: # iterate over the list # If the word is not already inside the dictionary's keys, create it if word not in frequency_words.keys(): frequency_words[word] = 1 else: frequency_words[word] += 1 return frequency_words