Question

I have the following code, which translates the input string into morse code. My code runs through every letter in the string and then through every character in the alphabet. This is very inefficient, because what if I was reading from a very large file, instead of a small alphabet string. Is there any way that I could improve my code, Maybe using the module re, to match my string with the morse code characters?

morse_alphabet = ".- -... -.-. -.. . ..-. --. .... .. .--- -.- .-.. -- -. --- .--. --.- .-. ... - ..- ...- .-- -..- -.-- --.."
ALPHABET = "abcdefghijklmnopqrstuvwxyz"
morse_letters = morse_alphabet.split(" ")
result = []
count_character = 0


def t(code):

    for character in code:
        count_letter = 0

        for letter in ALPHABET:
            lower_character = code[count_character].lower()
            lower_letter = letter.lower()

            if lower_character == lower_letter:

                result.append(morse_letters[count_letter])

            count_letter += 1

        count_character += 1

    return result

Answer 1

You can use string.ascii_lowercase together with zip() to make a dictionary instead:

import string
morse_alphabet = ".- -... -.-. -.. . ..-. --. .... .. .--- -.- .-.. -- -. --- .--. --.- .-. ... - ..- ...- .-- -..- -.-- --.."
morse_letters = dict(zip(string.ascii_lowercase, morse_alphabet.split()))

def t(code):
    return filter(None, (morse_letters.get(c.lower()) for c in code))

The t function is reduced to a filter() and a generator expression looping over each character in the input code.

The morse_letters dictionary now makes for a very fast lookup of codes, the filter() removes the None results for anything that isn’t a letter.

Result:

>>> t('S.O.S.')
['...', '---', '...']
>>> t('Stack Overflow')
['...', '-', '.-', '-.-.', '-.-', '---', '...-', '.', '.-.', '..-.', '.-..', '---', '.--']