Python Iterative Fibonacci [关闭]

Question

听着，我知道有关于此的一千个帖子，我花了三个小时看着它们。我知道这个代码不起作用的原因很简单，但我无法弄明白。当它运行时，我只希望它返回第n个术语。我是python的新手，也许有一些我没有得到的逻辑。所以当我这样做时：

n = int(input("What Fibonacci number would you like to find? "))

def fib(n):
    i = 0
    present = 1
    previous = 0

    while i < n:
        nextterm = present + previous
        present = previous
        previous = nextterm
        i = i + 1
        print nextterm

print(fib(n))

我明白了：

1
1
2
3
5
None

当我这样做：

n = int(input("What Fibonacci number would you like to find? "))

def fib(n):
    i = 0
    present = 1
    previous = 0

    while i < n:
        nextterm = present + previous
        present = previous
        previous = nextterm
        i = i + 1
        return nextterm

print(fib(n))

我只是得到“1”

我花了这么多时间在这上面，我很困惑。有人请修理我！

Answer 1

你只是忘了返回值：

n = int(input("What Fibonacci number would you like to find? "))

def fib(n):
    i = 0
    nextterm = 1
    present = 1
    previous = 0

    while i < n:
        nextterm = present + previous
        present = previous
        previous = nextterm
        i = i + 1
        #print nextterm

    return nextterm

print(fib(n))

Answer 2

因为return只返回一次，第一次返回完成，

更清楚的例子：

 def f():
     return 'good'
     return 'bad'

现在：

print(f())

返回：

'good'

另一方面，这也是一种解决方法：

n = int(input("What Fibonacci number would you like to find? "))

def fib(n):
    l=[]
    i = 0
    present = 1
    previous = 0

    while i < n:
        nextterm = present + previous
        present = previous
        previous = nextterm
        i = i + 1
        l.append(nextterm)
    return '\n'.join(str(i) for i in l)
print(fib(n))

或者print不做另外打印：

n = int(input("What Fibonacci number would you like to find? "))

def fib(n):
    i = 0
    present = 1
    previous = 0

    while i < n:
        nextterm = present + previous
        present = previous
        previous = nextterm
        i = i + 1
        print(nextterm)
fib(n)

Answer 3

在第一种情况下，你没有返回任何东西，所以当你print(fib(n))，因为python没有找到任何return语句，它返回None，这是你看到的最后一个打印，其他是循环内的那些。在第二种情况下，你在return循环中有while语句，所以当它执行第一次迭代时它返回1，离开帧并且没有执行其他迭代，所以它只打印'1'。

Answer 4

def fibonacci():
    num = int(input("How many numbers that generates?:"))
    i = 1
    if num == 0:
        fib = []
    elif num == 1:
        fib = [1]
    elif num == 2:
        fib = [1,1]
    elif num > 2:
        fib = [1,1]
        while i < (num - 1):
            fib.append(fib[i] + fib[i-1])
            i += 1
    return fib
print(fibonacci())