Python 重新启动循环

Question

How can I restart the loop in the following code after it hits 1 since in 3N+1 it goes 1>4>2>1?

Code:

import math
import random
num = 1
NumTF = False
play = True
while play:
  if num % 2 == 0:
    num = num / 2
  else:
    num = 3 * num + 1
print(num)
if num == 1:
  play = False
if play == False:
  num += 1 and play == True

Answer 1

I'm assuming that you want to end the loop, because...Collatz Conjecture.

All you have to do is add this simple if statement to the end:

elif num == 1:
    play = False

after the if num%2 == 0 statement, so the while loop ends. Currently, your doing this after your doing num = 3*num+1 , which makes it 4, so that case never happens. as rv.kvetch mentioned, the play==True does unexpected things, so just delete everything after print(num) , as those are unnecessary.