CODEWITHSUNDEEP
python
user11244958
user11244958

Reputation:

How to use another function to break out of a while loop under certain conditions?

I'm trying to use another function running in my while loop to break out of it under certain conditions. I have been writing practice code to try attempt it but it doesn't seem to break... it just keeps running infinitely

global test

def is_True():
    test = True

for i in range(5):
    test = False
    print("Run number:",i)

    while(test==False):
        print("the is_True method hasn't been called yet")
        is_True()
        print("The is__True method was called")

Upvotes: 4

Views: 324

Answers (5)

rawplutonium
rawplutonium

Reputation: 386

Here is a work around I've seen :

First, allow the method is_True to have a return type, a boolean, True/False, i.e:

def is_True():
    test = True
    return test

Then, allow the while loop to reinitialize the variable test to the return type of is_True i.e :

        print("The is_True method hasn't been called yet")
        test = is_True()

This is because, I suspect, the variable in the method is_True is private and only available within that method. Thus it doesn't affect the state of your global variable : test . Overall, the program should resemble this: 

global test

def is_True():
    test = True
    return test

for i in range(5):
    print("Run number:",i)
    test = False
    while(test==False):
        print("The is_True method hasn't been called yet")
        test = is_True()
        print("The is_True method was called")

I hope this answers your question, and happy coding!

Upvotes: 0

Nick Vitha
Nick Vitha

Reputation: 476

The problem here is that the test variable is being defined as a local variable in the function is_true() and is not using the global variable test. The simplest way to solve this would be to tell python to use the global variable test. You do that by changing:

test = True

to 

global test 
test = True

That is not, however, the best way to go about this. The best way to go about this would be to do what @Vasilis D or @Colin suggest, which would be to return a value from the is_True() function and use that instead:

def is_True():
    return True

for i in range(5):
    test = False
    print("Run number:",i)

    while(test==False):
        print("the is_True method hasn't been called yet")
        test = is_True()
        print("The is__True method was called")

Using global variables is, in general, frowned upon because it can create confusing situations where you define two different variables with the same name and are unsure of which one you're modifying.

Upvotes: 1

CoffeeTableEspresso
CoffeeTableEspresso

Reputation: 2652

A lot of the other answers mention how to fix this, but I figured it would also be helpful to explain why this isn't working, to help in the future.

In is_True, when you assign to test, you're making a new local variable, instead of refering to the global variable named test. If you want to refer to the global, add global test to the start of is_True. This will tell python that you want to refer to the global variable, not make a new local.

Of course, you probably shouldn't be using global variables for this, so a better solution is to return True from is_True() and do test = is_True().

Upvotes: 1

chepner
chepner

Reputation: 532268

You put the global statement in the wrong place. It goes in the function to indicate that test is not a local variable. A global statement at the global scope is basically a no-op.

def is_True():
    global test
    test = True

That said, try to avoid global variables when possible. Have is_True return True instead and assign the return value to test in the calling scope.

def is_True():
    return True

while not test:
    print("...")
    test = is_True()
    print("...")

Upvotes: 6

Vasilis D
Vasilis D

Reputation: 111

Modify the is_True() function:

def is_True():
    return True

and, inside the loop, assign it to test:

test = is_True()

Upvotes: 3

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