Pangram detection

beginner here-- Given a string, my code must detect whether or not it is a pangram. Return True if it is, False if not.It should ignore numbers and punctuation.

When given "ABCD45EFGH,IJK,LMNOPQR56STUVW3XYZ" it returns none and when given "This isn't a pangram! is not a pangram." it returns True when the answer should be False.

This isn't a pangram! is not a pangram. What am I not seeing?

import string

def is_pangram(s):
    singlechar = set(s)
    list = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']
    for index, item in enumerate(singlechar):
        if item in list:
            list.remove(item)
            if list:
                return True
                break 
    if not list:
        return False

Solution

You could have just continued to use sets and their method .difference to find out if there were more characters in the set of all characters or there were no differences (before that you would need to strip the string from punctuation (and whitespace) and make it lowercase (done by .lower and .translate and .maketrans methods of strings)):

import string


def is_pangram(s):
    input_set = set(s.lower().translate(
        str.maketrans('', '', f'{string.punctuation} ')))
    check_set = set(string.ascii_lowercase)
    return not check_set.difference(input_set)


value1 = 'The quick brown fox jumps over a lazy dog!'
print(is_pangram(value1))
# True

value2 = 'This isn\'t a pangram! is not a pangram'
print(is_pangram(value2))
# False

If you want to still do it with a list:

def is_pangram(s):
    input_set = set(s.lower().translate(
        str.maketrans('', '', f'{string.punctuation} ')))
    lst = list(string.ascii_lowercase)
    for item in input_set:
        if item in lst:
            lst.remove(item)
            if not lst:
                return True
    return False