求斐波那契数的python语言实现---递归和迭代

def fab(n):
        n1 = 1
        n2 = 1
        if n<1:
                print("输入有误!")
                return -1
        while (n-2)>0:
                n3 = n2+n1
                n1 = n2
                n2 = n3
                n-=1
        return n3
number = int(input("请输入要求的斐波那契数的第几个数:"))
result = fab(number)
print(result) 

def fab(n):
    if n==1 or n==2:
        f = 1
    else:
        f = fab(n-1)+fab(n-2)
    return f
number = int(input("请输入要求的斐波那契数的第几个数:"))
result = fab(number)
print(result)