如何以适当的方式在一系列数字上加逗号

def add_commas(number):
    # 将数字转换为字符串
    number_str = str(number)

    # 检查数字是否为负数
    negative = False
    if number_str[0] == "-":
        negative = True
        number_str = number_str[1:]  # 去除负号

    # 处理小数部分
    decimal_index = number_str.find(".")
    if decimal_index != -1:
        decimal_part = number_str[decimal_index:]
        number_str = number_str[:decimal_index]

    # 从右向左每三位插入逗号
    comma_index = len(number_str) - 3
    while comma_index > 0:
        number_str = number_str[:comma_index] + "," + number_str[comma_index:]
        comma_index -= 3

    # 如果是负数，将负号放在最前面
    if negative:
        number_str = "-" + number_str

    # 如果有小数部分，重新拼接
    if decimal_index != -1:
        number_str += decimal_part

    return number_str

# 示例用法
number = 1234567.89
formatted_number = add_commas(number)
print(formatted_number)  # 输出: 1,234,567.89