初学者迭代python

#汉诺塔
def hanni(n,A,B,C):
    if n == 1:
        print (A,'-->',C)
    else:
        # 将n-1个盘子移动到B上
        hanni(n-1,A,C,B)
        # 将第n个移动到C上
        print(A,'-->',C)
        # 将n-1个移动到C上
        hanni(n-1,B,A,C)

hanni(3,'A','B','C')
#阶乘
#迭代
def factorial(N):
    F = 1
    for i in range(1,N+1):
        F *= i
    return F
#递归
def factorial_recursion(N):
    if N == 1:
        return 1
    else:
        F = N * factorial_recursion(N -1)
    return F

print factorial(10)
print factorial_recursion(10)
#斐波那契数列
#迭代
def fib_ite(N):
    n1 = 1
    n2 = 1
    n3 = 1
    if N < 1:
        print 'plesae a num'
        return -1

    while (N-2) > 0:
        n3 = n1 + n2
        n1 = n2
        n2 = n3
        N -= 1
    return n3
#递归
def fib_num(N):
    if N == 1 or N == 2:
        return 1
    else:
        return fib_num(N-1)+fib_num(N-2)

print fib_num(20)

print fib_ite(20)