python之如何创建递归函数来计算斐波那契数列

def fib(n): 
    if n == 0: 
        return 0 
    elif n ==1: 
        return 1 
    else: 
        return fib (n-1) + fib (n-2) 

如何使这个递归？当我运行程序并输入一个数字时，返回相同的数字

请您参考如下方法:

您的函数已经是递归的。您只需传入 0、1 或 5 以外的数字即可查看效果:

>>> def fib(n): 
...     if n == 0: 
...         return 0 
...     elif n ==1: 
...         return 1 
...     else: 
...         return fib (n-1) + fib (n-2) 
...  
>>> fib(0)  # returns immediately, because n == 0 
0 
>>> fib(1)  # returns immediately, because n == 1 
1 
>>> fib(2)  # returns fib(1) + fib(0) == 1 + 0 == 1 
1 
>>> fib(3)  # returns fib(2) + fib(1) == (fib(1) + fib(0)) + 1 == (1 + 0) + 1 == 2 
2 
>>> fib(100) # returns fib(99) + fib(98) == (fib(98) + fib(97)) + (fib(97) + fib(96)) == ... 
# This one takes a while because 2**100 calculations need to be completed 
354224848179261915075