斐波那契数列：1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, ... 如果设F(n）为该数列的第n项（n∈N*），那么这句话可以写成如下形式：:F(n)=F(n-1)+F(n-2) 显然这是一个线性递推数列

FBNQ

def fib_iter(n):
    pre,next = 1, 1
    result = 0
    i = 2
    while i < n:
        result = pre + next
        pre,next= next,result
        
        i += 1
    return result

def fab(max): 
    n, a, b = 0, 0, 1 
    L = [] 
    while n < max: 
        L.append(b) 
        a, b = b, a + b 
        n += 1 
    return L
    
def fibonacci3(num):
    a, b = 0, 1
    for i in range(1, num+1):
        a, b = b, a+b
    return b
    
    
def fab(num): 
    n, a, b = 0, 0, 1 
    while n < num: 
        yield b 
        # print b 
        a, b = b, a + b 
        n += 1