如何修复我的递归倒计时 python 函数的代码，以便它只打印“LIFT OFF！” 一次？

Question

#!/usr/bin/env python

import time

def countdown(num):
  if num <= 0:
    return num
  else:
    time.sleep(0.1)
    print(num)
    countdown(num - 1)
    print(“LIFT OFF!”)

Answer 1

这应该有效：

#!/usr/bin/env python

import time

def countdown(num):
  if num <= 0:
    print('LIFT OFF!')
    return num
  else:
    time.sleep(0.1)
    print(num)
    countdown(num - 1)

这是输出：

>>> countdown(4)
4
3
2
1
LIFT OFF!
>>> 

Answer 2

如果你只是想lift off打印一次，然后打印一次：

import time

def countdown(num):
  if num <= 0:
    return num
  else:
    time.sleep(0.1)
    print(num)
    countdown(num - 1)

countdown(5)
print('LIFT OFF!')

输出：

5
4
3
2
1
LIFT OFF!

现在countdown()函数只做一件事，即在延迟后打印数字。