My solution for Cassidy Williams' weekly interview problem for the week of May 4, 2020

oneRow.py

KEYBOARD_ROWS = {
    'qwerty': (tuple('qwertyuiop'), tuple('asdfghjkl'), tuple('zxcvbnm')),
    'dvorak': (tuple('pyfgcrl'), tuple('aoeuidhtns'), tuple('qjkxbmwvz')),
    'colemak': (tuple('qwfpgjluy'), tuple('arstdhneio'), tuple('zxcvbkm')),
}

LETTERS_TO_ROWS = {}
for keyboard in KEYBOARD_ROWS:
    LETTERS_TO_ROWS[keyboard] = {}
    for row in KEYBOARD_ROWS[keyboard]:
        for letter in row:
            LETTERS_TO_ROWS[keyboard][letter] = row

def oneRow(words, keyboard='qwerty'):
    '''
    Given an array of words, returns the words that can be typed using letters of only one row on a keyboard.
    Limitations: does not consider punctuation characters in a word.
    '''
    assert (keyboard in KEYBOARD_ROWS), "unsupported keyboard, supported: " + ', '.join(KEYBOARD_ROWS)
    letters_to_rows = LETTERS_TO_ROWS[keyboard]
    return list(filter(lambda word: len(word) and all(letters_to_rows[l] == letters_to_rows[word[0]] for l in word), words))

if __name__ == "__main__":
    print(oneRow(['candy', 'doodle', 'pop', 'shield', 'lag', 'typewriter']))