基于数字部分的Python字符串处理:'5a + 6b'+'2a + 3b + 9c'='7a + 9b + 9c'

import re

def calculate_expression(expression):
    # 使用正则表达式提取数字和字母
    pattern = r'(\d+[a-z]+)'
    numbers = re.findall(pattern, expression)

    # 将字母和数字分离
    letters = re.findall(r'[a-z]', expression)
    numbers = re.findall(r'\d+', expression)

    # 将字母和数字组合成字典
    result = {}
    for i in range(len(letters)):
        result[letters[i]] = int(numbers[i])

    # 计算表达式
    for i in range(len(numbers)):
        for j in range(i+1, len(numbers)):
            if numbers[i] == numbers[j]:
                result[letters[i]] += result[letters[j]]
                result[letters[j]] = 0

    # 将结果转换为字符串
    output = ''
    for letter in result:
        if result[letter] != 0:
            output += str(result[letter]) + letter

    return output

expression = '5a + 6b + 2a + 3b + 9c'
result = calculate_expression(expression)
print(result)