Ndtyjky

I know this has been asked before on this site, but I was unable to understand the answers given (I'm still very new), so I'm going to try and ask again. My assignment is to write code that takes a 10 digit phone number (XXX-XXX-XXXX) and converts any letters (i.e. 800-FLO-WERS) to numbers. I've wracked my brain on this, and could really use some help/explanations. In the class I'm taking (using the excellent "Starting out with Python, 4th edition, by Tony Gaddis), I cannot use concepts we have not covered (like dictionaries), but I can use lists/tuples. The code I've come up with follows:

def main():

    try:

        user_number = str(input('Enter a phone number (XXX-XXX-XXXX): ')).upper()

        converted_number = check_number(user_number)

        print('The phone number is:',converted_number

    except Exception as err:

        print(err)

def check_number(user_number):

    try:

        for char in user_number:

            if char.isalpha():

                result = convert_to_num(char)

                return result

            else:

                return char

        return converted_number

    except Exception as err:

        print(err)

def convert_to_num(char):

    if char in ['A','B','C']:

        char = 2

    elif char in ['D','E','F']:

        char = 3

    elif char in ['G','H','I']:

        char = 4

    elif char in ['J','K','L']:

        char = 5

    elif char in ['M','N','O']:

        char = 6

    elif char in ['P','Q','R','S']:

        char = 7

    elif char in ['T','U','V']:

        char = 8

    elif char in ['W','X','Y','Z']:

        char = 9

    return char

main()

Obviously, I'm not sure how to store the converted letter-to-number (considered doing it by indexing, but couldn't quite make that work either). I'm not looking for anyone to do my work for me, but a detailed explanation of what I'm doing wrong would be lovely.

The purpose of return is to return to the function where it was called. Here since return is inside the loop. It will exit the function in the first iteration.

for char in user_number:

     if char.isalpha():

           result = convert_to_num(char)

           return result

     else:

           return char

     return converted_number

Just use a list instead to store the converted values then return them after the loop using the join() method.

def main():

    try:

        user_number = str(input('Enter a phone number (XXX-XXX-XXXX): ')).upper()

        converted_number = check_number(user_number)

        print('The phone number is:',converted_number)

    except Exception as err:

        print(err)



def check_number(user_number):

    try:

        r = 

        for char in user_number:

            if char.isalpha():

                result = convert_to_num(char)

                r.append(str(result))

            else:

                r.append(char)

        return "".join(r)

    except Exception as err:

        print(err)



def convert_to_num(char):

    if char in ['A','B','C']:

        char = 2

    elif char in ['D','E','F']:

        char = 3

    elif char in ['G','H','I']:

        char = 4

    elif char in ['J','K','L']:

        char = 5

    elif char in ['M','N','O']:

        char = 6

    elif char in ['P','Q','R','S']:

        char = 7

    elif char in ['T','U','V']:

        char = 8

    elif char in ['W','X','Y','Z']:

        char = 9

    return char

main()

If you can't use join()

def check_number(user_number):

    try:

        r = ''

        for char in user_number:

            if char.isalpha():

                result = convert_to_num(char)

                r += str(result)

            else:

                r += char

        return r

    except Exception as err:

        print(err)

This code:

if char.isalpha():

    result = convert_to_num(char)

    return result

else:

    return char

Will return immediately with a single digit as the result. You want to return a string of all of the digits, not just the first digit, so you need to store the output digits and eventually return all of them (after the for loop is done) as a single string.

Initializing an empty list output = and appending the output digits to it after each iteration of the for loop, then returning the joined list (using "".join()) is a good way to accomplish this.

If you aren't allowed to use "".join(), you can also just build up a string (output = "" and output += char) and return it directly, but this will be slower.