用python写斐波那契数列求和程序

下面是用 Python 实现斐波那契数列求和的示例代码：

def fibonacci_sum(n):
    if n <= 0:
        return 0
    elif n == 1:
        return 1
    else:
        a, b = 0, 1
        total = 0
        for i in range(n-1):
            a, b = b, a + b
            total += a
        return total