Question

Python coding:

 HW `declaration.py` 
  * define function `calc_histogram(lines)`
  * returns histogram dictionary and total non-whitespace characters
  * takes list of strings as argument
  * ignore comment lines denoted by `#`
  * if invoking script directly, load `data/declaration.txt` and calculate histogram
  * print histogram by sorted characters
  * count letter instances not characters, so `A` and `a` count as same

(This is the local test I was given):

if __name__ == '__main__':
    import os.path
    file_path = os.path.join("data", 'declaration.txt')
    print(file_path)

    letter = open(file_path)
    text = letter.readlines() # Read entire file into a list of strings
    letter.close()  # If you open it, close it!

    hist, count = calc_histogram(text)

    keys = list(hist.keys())
    keys.sort()
    print("Keys:", keys)
    sum = 0.0
    for a in keys:
        val = 100.0*(hist[a]/count)
        print("{} : {:4d} : {:7.3f}%".format(a, hist[a], val))
        sum += val

    print("total={:.5f}\ncnt={}".format(sum, count))

Answer 1

First we define an empty dictionary and iterate through each line in the given list:

hist = {}  # define an empty dictionary to store character occurrences
for line in text:  # iterate through each line in the list
     line = line.strip()  # remove trailing newline characters

After that, we remove all the comments:

    hist = {}  # define an empty dictionary to store character occurrences
    for line in text:  # iterate through each line in the list
        line = line.strip()  # remove trailing newline characters

        # if comments are present, remove the part of the sentence
        # from # to the end of the line
        if "#" in line:
            index = line.find("#")
            line = line[:index]

Now we change the case of the line to lower and remove all the spaces:

    hist = {}  # define an empty dictionary to store character occurrences
    for line in text:  # iterate through each line in the list
        line = line.strip()  # remove trailing newline characters

        # if comments are present, remove the part of the sentence
        # from # to the end of the line
        if "#" in line:
            index = line.find("#")
            line = line[:index]

        line = line.lower()  # change to lower case as the question is case insensitive
        line = line.replace(" ", "")  # remove all the whitespaces in the line

Now we add the occurances to the dictionary:

for character in line:
    try:
        hist[character] += 1
    except KeyError:
        hist[character] = 1

The entire function is given below:

def calc_histogram(text):
    hist = {}  # define an empty dictionary to store character occurrences
    for line in text:  # iterate through each line in the list
        line = line.strip()  # remove trailing newline characters

        # if comments are present, remove the part of the sentence
        # from # to the end of the line
        if "#" in line:
            index = line.find("#")
            line = line[:index]

        line = line.lower()  # change to lower case as the question is case insensitive
        line = line.replace(" ", "")  # remove all the whitespaces in the line

        # if the character is already present in the dictionary, increment the count,
        # else set the count of that character to 1. Since the characters are considered as
        # the keys in the dictionary, we get a KeyError when that particular character is
        # not in the dictionary
        for character in line:
            try:
                hist[character] += 1
            except KeyError:
                hist[character] = 1

    # return the hist dictionary and the sum of all the occurrences of each non-whitespace character
    return hist, sum(list(hist.values()))

Good luck!