"""
 count_words.py

 Read words.txt which has one word per line.
 Count how many times each word appears
 and print a summary.

 Tested with python 2.7.

   $ python count_words.py
   -- count_words --
     12 cat          
      2 dog          
      2 duck         
      1 elephant     
      3 mouse        
"""

def get_words(filename):
    """ return a list of words from a file with one word per line """
    # file = open(filename)
    # words = file.read()      # get file as string
    # no_newlines = words.split('\n')  # split at newlines
    # no_blanks = filter(None, no_blanks)  # remove ''
    # return no_blanks
    # ... or all of that in one expression.
    return filter(None, open(filename).read().split('\n'))

def count(words):
    """ Return a dictionary of { word : how_many_times } """
    how_many = {}
    for word in words:
        how_many[word] = how_many.get(word, 0) + 1
    return how_many

def main():
    print '-- count_words --'
    words = get_words('words.txt')
    print "words = {}".format(words)
    counts = count(words)
    print "counts = {}".format(counts)

if __name__ == '__main__':
    import doctest
    doctest.testmod()
    main()