Returning empty list

May 14, 2023

Hi I have problem with my program, I try to check which letters in alphabet doesn’t appear in list, unluckily it returns empty list I don’t know why

I tried many ways but it still doesn’t work…

import string
def get_missing_letters(s):
    missing =[]
    alphabet = list(string.ascii_lowercase)
    s = list(s)
    for letter in s:
        if letter not in alphabet:
            missing.append(letter)
        return missing
print(get_missing_letters("abcdefgpqrstuvwxyz"))

>Solution :

You have two issues, the return happens after the first iteration and you are actually checking if the letters in your string exists in ascii_lowercase instead of the opposite

def get_missing_letters(s):
    missing = []
    s = list(s)
    for letter in list(string.ascii_lowercase):
        if letter not in s:
            missing.append(letter)
    return missing


print(get_missing_letters("abcdefgpqrstuvwxyz"))
# ['h', 'i', 'j', 'k', 'l', 'm', 'n', 'o']

Another way to find the diff is to use set

def get_missing_letters(s):
    return set(string.ascii_lowercase).difference(s)
    # or
    return set(string.ascii_lowercase) - set(s)

print(get_missing_letters("abcdefgpqrstuvwxyz"))
# {'j', 'n', 'k', 'l', 'i', 'm', 'o', 'h'}

You can sort it if the order is important to you

def get_missing_letters(s):
    missing = set(string.ascii_lowercase).difference(s)
    return sorted(missing)


print(get_missing_letters("abcdefgpqrstuvwxyz"))
# ['h', 'i', 'j', 'k', 'l', 'm', 'n', 'o']