python编写程序，输入4个数，求出它们的平均数并输出，要求保留小数点后2位。（输出时用3种方式实现保留小数点后两位操作）

在Python中，计算四个数的平均值并保留小数点后两位有多种方法。以下是三种常见的实现方式：

1. 使用`round()`函数直接处理：

def average(numbers):
    total = sum(numbers)
    avg = round(total / len(numbers), 2)
    print("Average (using round):", avg)

numbers = [float(input(f"请输入第{i+1}个数: ")) for i in range(4)]
average(numbers)

2. 利用f-string格式化输出：

def average(numbers):
    total = sum(numbers)
    avg = total / len(numbers)
    print(f"Average (format string): {avg:.2f}")

numbers = [float(input(f"请输入第{i+1}个数: ")) for i in range(4)]
average(numbers)

3. 使用`decimal`模块处理高精度浮点数：

from decimal import Decimal

def average(numbers):
    total = sum(Decimal(num) for num in numbers)
    avg = total / Decimal(len(numbers))
    print("Average (decimal module): {:.2f}".format(avg))

numbers = [float(input(f"请输入第{i+1}个数: ")) for i in range(4)]
average(numbers)