用python求斐波那契数列和斐波那契数列和

以下是两种Python求斐波那契数列和的例子：

1. 求斐波那契数列前n项和

def fibonacci_sum(n):
    if n <= 0:
        return 0
    elif n == 1:
        return 1
    else:
        a, b = 0, 1
        sum = 1
        for i in range(2, n+1):
            c = a + b
            sum += c
            a, b = b, c
        return sum

# 示例
print(fibonacci_sum(10)) # 输出：143

2. 求斐波那契数列第n个数的值

def fibonacci(n):
    if n <= 0:
        return 0
    elif n == 1:
        return 1
    else:
        a, b = 0, 1
        for i in range(2, n+1):
            c = a + b
            a, b = b, c
        return b

# 示例
print(fibonacci(10)) # 输出：55