converting individual digits to string

Question

I think i\'m very close but i cant seem to fix my issues. I need a function that takes a 10-digit input from user (me) and sets each letter to is numeric value.

Example:

Answer 1

I think it's easiest to pre-calculate the number character for each letter.

# len(keys) == 26 so that the index of a letter
# maps to its phone key
keys =           ['2']*3 + ['3']*3 \
     + ['4']*3 + ['5']*3 + ['6']*3 \
     + ['7']*4 + ['8']*3 + ['9']*4

def letter_to_key(x):
    if x.isalpha():
        # calculate the 'index' of a letter.
        # a=0, b=1, ..., z=25
        index = ord(x.lower()) - ord('a')
        return keys[index]
    # If it's not a letter don't change it.
    return x

def translate_digits(phone_num):
    return ''.join(map(letter_to_key, phone_num))

print(translate_digits('941-019-abcd'))