True while loop python

Question

I've been trying to understand this for a while now and I don't get why the true while loop doesn't exit when the check() function returns False value and asks input(i.e "enter input")again and again but it exits when else statement of func() function returns False value. No matter what,as far as I know, the while loop should stop or exit when the value returned is false, but that isn't the case here. I don't intend to modify the code but would just like to understand the concept behind this. please help me. Thanks! in advance.

def check(num):

    if(num%2==0):
        return True
    else:
        return False

def func():

    temp=[str(i) for i in range(1,51)]
    while True:
        c=input("enter input: ")
        if c in temp:
            c=int(c)
            if check(c):
                print(c)
                break
        else:
            print("input invalid, enter only digits from 1 to 50")
            return False

Your code doesn't have any return statement, or other way to end the loop, when the if c in temp condition passes but the if check(c) one doesn't. Try following the logic yourself, step by step, if this is unclear — Robin Zigmond
– Robin Zigmond, Commented Jun 20, 2020 at 12:05
Note that your check function can just return num % 2 == 0 . — Péter Leéh
– Péter Leéh, Commented Jun 20, 2020 at 12:43

energetics pythonista · Accepted Answer · 2020-06-20 12:24:10Z

1

It would most likely be due to the fact that the while true loop being used in the func() function is local to that function and so when you try to use the other function check() to actually change the value, it cannot do so. It would only be able to return false or true for a while loop that is included in the same function.

answered Jun 20, 2020 at 12:24

energetics pythonista

437 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

un random · Accepted Answer · 2020-06-20 12:03:45Z

0

To exit a loop (for or while) outside a function or exit within the funtion but only exiting the loop you should use break instead of return.

answered Jun 20, 2020 at 12:03

un random

3011 silver badge9 bronze badges

Comments

Sumuk Shashidhar · Accepted Answer · 2020-06-20 12:05:58Z

0

The blank return that you have doesn't actually do anything.

You will have to break from the loop.

It works in the second case as you actually return a value like False

answered Jun 20, 2020 at 12:05

Sumuk Shashidhar

19011 bronze badges

Comments

energetics pythonista · Accepted Answer · 2020-06-20 12:12:31Z

0

You could try doing this:

loop = True

def check(num):
  global loop
  if(num%2==0):
    loop = False
  else:
    loop = False

def func():
  global loop
  temp=[str(i) for i in range(1,51)]
  while loop:
    c=input("enter input: ")
    if c in temp:
        c=int(c)
        if check(c):
            print(c)
            loop = False 
    else:
        print("input invalid, enter only digits from 1 to 50")
        loop = False

answered Jun 20, 2020 at 12:12

energetics pythonista

437 bronze badges

1 Comment

TechBee Over a year ago

thank you! but i actually don't intend to exit the loop, i just want to understand the concept behind why does the loop exit when func() function returns false value and doesn't exit when the same false value is returned by check() function.

Collectives™ on Stack Overflow

True while loop python

4 Answers 4

Comments

Comments

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related