Python实现分数序列求和

#!/usr/bin/env python

# coding:UTF-8

  

  

"""

@version: python3.x

@author:曹新健

@contact: 617349013@qq.com

@software: PyCharm

@file: 1223.py

@time: 2018/12/23 20:56

"""

  

'''

有一分数序列：2/1，3/2，5/3，8/5，13/8，21/13...求出这个数列的前20项之和。

'''

"""

#方法一

def g(n):

  if n <= 2:

    return n

  else:

    return g(n-1) + g(n-2)

sum = 0

for i in range(1,21):

  sum += g(i+1)/g(i)

print(sum)

"""

  

#方法二

numerator = 2

denominator = 1

sum = 0

while True:

  try:

    n = int(input("请输入一个整数："))

  except ValueError:

    print("输入错误，请输入整数")

  else:

    for i in range(n):

      sum += numerator / denominator

      numerator, denominator = numerator + denominator, numerator

  

    print(sum)

    break