concept vowel in category python

This is an excerpt from Manning's book Tiny Python Projects: Learn coding and testing with puzzles and games. Login to get full access to this book.

Your program should be called crowsnest.py. It will accept a single positional argument and will print the given argument inside the “Ahoy” bit, along with the word “a” or “an” depending on whether the argument starts with a consonant or a vowel.

Verify that the --vowel option is in the set of vowels “a,” “e,” “i,” “o,” and “u”

Replace all instances of vowels in the input text with the specified (or default) --vowel argument

I declared the new_char() function inside main() because I wanted to reference the vowel variable inside the function, as shown in figure 8.6. Because new_char() “closes” around the vowel, it is a special type of function called a closure.

Figure 8.6 The new_char() function can only be seen within the main() function. It creates a closure because it references the vowel variable. Code outside of main() cannot see or call new_char().

If we don’t write this as a closure, we will have to pass the vowel as an argument:

#!/usr/bin/env python3
"""Make rhyming words"""
 
import argparse
import re                                                                    #1
import string
 
 
# --------------------------------------------------
def get_args():
    """get command-line arguments"""
 
    parser = argparse.ArgumentParser(
        description='Make rhyming "words"',
        formatter_class=argparse.ArgumentDefaultsHelpFormatter)
 
    parser.add_argument('word', metavar='word', help='A word to rhyme')
 
    return parser.parse_args()
 
 
# --------------------------------------------------
def main():
    """Make a jazz noise here"""
 
    args = get_args()                                                        #2
    prefixes = list('bcdfghjklmnpqrstvwxyz') + (                             #3
        'bl br ch cl cr dr fl fr gl gr pl pr sc '
        'sh sk sl sm sn sp st sw th tr tw thw wh wr '
        'sch scr shr sph spl spr squ str thr').split()
 
    start, rest = stemmer(args.word)                                         #4
    if rest:                                                                 #5
 
        print('\n'.join(sorted([p + rest for p in prefixes if p != start]))) #6
    else:
        print(f'Cannot rhyme "{args.word}"')                                 #7
 
 
# --------------------------------------------------
def stemmer(word):
    """Return leading consonants (if any), and 'stem' of word"""
 
    word = word.lower()                                                      #8
    vowels = 'aeiou'                                                         #9
    consonants = ''.join(                                                    #10
        [c for c in string.ascii_lowercase if c not in vowels])
    pattern = (                                                              #11
        '([' + consonants + ']+)?' # capture one or more, optional
        '([' + vowels     + '])'   # capture at least one vowel
        '(.*)'                     # capture zero or more of anything
    )
 
    match = re.match(pattern, word)                                          #12
    if match:                                                                #13
        p1 = match.group(1) or ''                                            #14
        p2 = match.group(2) or ''
        p3 = match.group(3) or ''
        return (p1, p2 + p3)                                                 #15
    else:
        return (word, '')                                                    #16
 
 
# --------------------------------------------------
def test_stemmer():                                                          #17
    """test the stemmer"""
 
    assert stemmer('') == ('', '')
    assert stemmer('cake') == ('c', 'ake')
    assert stemmer('chair') == ('ch', 'air')
    assert stemmer('APPLE') == ('', 'apple')
    assert stemmer('RDNZL') == ('rdnzl', '')
    assert stemmer('123') == ('', '')
 
 
# --------------------------------------------------
if __name__ == '__main__':
    main()

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