# "Serial/Ordinal" number conversion
ordinal_endings = ["st", "nd", "rd", "th"]
BASE_CHAR_POS = ord('a') - 1

def get_last_digit(num):
    return num%10

def get_char_pos(char):
    # Conditional expression will check whether or not char
    # is a string that needs to be converted into its ascii
    # value, or if the ascii value has already been passed.
    return (ord(char) if isinstance(char, str) else char) - BASE_CHAR_POS

def get_ordinal(num):
    last_digit = get_last_digit(num)

    ordinal = str(num)
    ordinal_suffix = None

    # Specific cases for "teens"
    if (num > 10 and num < 21):
        ordinal_suffix = ordinal_endings[3]
    elif last_digit >= 1 and last_digit <= 3:
        ordinal_suffix = ordinal_endings[last_digit-1]
    else:
        # For numbers with last digit 0 or =/= 1,2,3
        ordinal_suffix = ordinal_endings[3]

    return ordinal + ordinal_suffix

while True:
    try:
        # Passing input to ord is a way we can type check
        # for a character, without doing it explicitly.
        input_char_val = ord(input("Enter a character:> "))
    except:
        continue

    char_pos = get_char_pos(input_char_val)
    print("The ordinal position of this character is:", get_ordinal(char_pos))