'''Program to print out a word count dictionary for a given file.'''

import re

FILENAME_PROMPT = 'Enter filename: '
WORD_MATCHER = '[a-zA-Z]+'

def extract_words(gizmo):
    '''Returns a list of all the words contained in filename.'''
    input_file = open(gizmo, 'r')
    source_string = input_file.read().lower()
    input_file.close()
    words = re.findall(WORD_MATCHER, source_string)
    return words


def build_word_dict(word_list):
    '''Constructs and returns a dictionary of words in word_list to their
    occurrence counts.'''
    word_dict = {}
    for word in word_list:
        if word in word_dict:
            word_dict[word] += 1
        else:
            word_dict[word] = 1
    return word_dict


def print_dictionary(dict_to_print):
    '''Print out the contents of the given word count dictionary
    in alphabetical order.'''
    for word, count in sorted(dict_to_print.items()):
        print("Word '{0}' appeared {1} times".format(word, count))
    

def main():
    '''Ask for a filename, then construct and print out a listing of
    the number of occurrences of each word in the filename.'''
    filename_to_read = input(FILENAME_PROMPT)
    words_in_file = extract_words(filename_to_read)
    constructed_dict = build_word_dict(words_in_file)
    print_dictionary(constructed_dict)
    
    
main()