Question

Define a function file_to_hist() which takes a string representing a filename, opens the file, reads its contents, closes the file,* and returns a histogram based on the letter frequencies in the given file. If no such file exists, your function should return an empty histogram (i.e., an empty dictionary {}). So for example, if the file nash.txt was in the same directory as char_hist3.py and had the following contents:

I have never seen a purple cow,
And I never hope to see one.
But I can tell you anyhow,
I'd rather see than be one.

Then file_to_hist("nash.txt") would return the following histogram: {'r': 5, 'w': 2, 't': 5, ',': 2, 'u': 3, 'o': 7, 'B': 1, 'b': 1, 'p': 3, 's': 3, 'd': 2, 'l': 3, '\n': 4, 'A': 1, 'h': 5, '.': 2, 'n': 9, 'a': 6, 'v': 3, 'y': 2, ' ': 22, 'I': 4, "'": 1, 'c': 2, 'e': 18}.

You must use the provided make_hist() function in your definition.

You should be using with and as to make sure that the file gets closed automatically. You do not need to use .close()

def make_hist(string):
    """
    returns a histogram based on the given string.
  
    str -> histogram
    """
    hist = {}
    for char in string:
        if char in hist:
            hist[char] += 1
        else:
            hist[char] = 1
    return hist

Answer 1

Python program :

import os

def make_hist(string):
    """
    returns a histogram based on the given string.
  
    str -> histogram
    """
    hist = {}
    for char in string:
        if char in hist:
            hist[char] += 1
        else:
            hist[char] = 1
    return hist


def file_to_hist(filename):
    """
    this function returns a histogram based on the filename.
    if the filename exists then it gives the histogram of that file.
    otherwise it would return a empty dictionary {}.
    """
    histogram = {}
    if os.path.isfile(filename):
        with open(filename,'r') as f: # open a file using with
            lines = f.read()          # read all content of file into lines
            lines = lines + '\n' 
            histogram = make_hist(lines) # generates a histogram
            
    return histogram


print(file_to_hist("nash.txt")) # testing the function file_to_hist
        
        

Input file : nash.txt

Output :