Convert a string of numbers into a word

Question

I need to do a function that receives a string composed of digits between 2-9 and that the output are letters, that is, basically the function will work as a keyboard of a mobile phone, where the number '2' will match the 'A', the '22' will match the 'B', until 9999 matches Z. For example:

>>> def teclas('22 2 333 33')
"CAFE"

The values entered in the arguments can "turn around", in the sense that if '2222' is inserted, the letter will return to 'A', '22222' the letter will be 'B', etc. As it works on a keystroke mobile phone. Right now I have a dictionary where I assign all the numbers to the corresponding letters like this:

dic={'2':'A', '22':'B', '222':'C', '3':'D'....}

My doubt is how I do so that in case it is inserted '2222' as argument, it is assigned again the value 'A' (I do not know how I do the program "go around").

Answer 1

From your comments, I understand that you want to model a mobile keyboard.

If so, instead of a dictionary for all keys, you should have a vector for each one.

tecla2 = ("A", "B", "C")
tecla3 = ("D", "E", "F")
# demais teclas...

When the user clicks on a key, increment a counter and to find out which letter make the counter module with the vector size of the pressed key.

Your example of "2222", for example, would turn to "i += 4". Whereas the vector starts at 0: pos = (i - 1) %3. The result would be position 0, which has the "A" as you want.

When the user chooses another key, the counter must be reset.

Concept code below:

letras_tecla_2 = ("a", "b", "c")
letras_tecla_3 = ("d", "e", "f")

def string_from_teclas(teclas):
    ult_tecla = ""
    contador = 0
    string = ""

    for tecla in teclas:
        if tecla == ult_tecla:
            contador += 1
        elif ult_tecla != "":
            contador = contador % 3

            if ult_tecla == "2":
                string += letras_tecla_2[contador]
            elif ult_tecla == "3":
                string += letras_tecla_3[contador]

            contador = 0

        ult_tecla = tecla

    return(string)

print( string_from_teclas("22 222 3 33 ") )