将双精度数字截断为x个有效数字

def truncate_double_precision(number, x):
    # 将双精度数字转换为字符串
    number_str = str(number)
    
    # 获取小数点位置
    decimal_index = number_str.index('.')
    
    # 确定要保留的有效数字位数
    digits_to_keep = x + 1 if decimal_index >= 0 else x
    
    # 截取字符串中的有效数字部分
    truncated_str = number_str[:digits_to_keep]
    
    # 如果小数部分位数大于x，则根据第x+1位数字进行四舍五入
    if len(truncated_str) > x:
        last_digit = int(truncated_str[x])
        if last_digit >= 5:
            truncated_str = str(int(truncated_str[:x]) + 1)
        else:
            truncated_str = truncated_str[:x]
    
    # 如果小数部分位数小于x，则在末尾补零
    elif len(truncated_str) < x:
        truncated_str += '0' * (x - len(truncated_str))
    
    # 将截断后的字符串转换回双精度数字
    truncated_number = float(truncated_str)
    
    return truncated_number

# 示例用法
number = 3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679
x = 5
truncated_number = truncate_double_precision(number, x)
print(truncated_number)