如何计算字符串中的字母数并删除输出中的重复字母

def calculate_and_remove_duplicates(string):
    letter_count = {}
    
    for char in string:
        if char.isalpha():
            letter_count[char] = letter_count.get(char, 0) + 1
    
    result = ""
    
    for char in string:
        if char.isalpha() and letter_count[char] > 0:
            result += char
            letter_count[char] -= 1
    
    return result