While true loop not ending

Question

I have 3 functions. listener function calls check_url function in every 10 seconds. If this function success on checking, it calls destroy function. After destroy function done it's job, i want to terminate the listener I tried to do it with finish_control variable

def listener(url):
    while True:
        if finish_control == 1:
            break
        check_url(url)
        sleep(10)

def check_url(url):
    print ("Status: Listening")
    response = urllib.request.urlopen(url)
    data = response.read()
    text = data.decode('utf-8')
    if text == '1':
        print("--Action Started!--")
        destroy(argv.location)

def destroy(location):
    #some work
    print("---Action completed!---")
    finish_control = 1

But the while loop inside listener doesn't terminate. I also tried with

while (finish_control == 0):

There is also same problem. How can I make it stop after destroy finishes it's job?

`listener()` function does not "know" the `finish_control` variable — fedorqui, Mar 30 '15 at 19:32

score 3 · Accepted Answer · answered Mar 30 '15 at 19:31

3

Make sure finish_control is defined globally and in your destroy function add the following:

global finish_control

answered Mar 30 '15 at 19:31

Malik Brahimi

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i will mark it in few minutes it's not allow me now – JayGatsby Mar 30 '15 at 19:39

score 3 · Answer 2 · answered Mar 30 '15 at 19:32

3

The problem is finish_control in function destroy is local to the function. The finish_control in listener is not the same variable. The work around for this is to return the values as in

In your destroy method add a line return 1 instead of finish_control = 1
add a return before destroy(argv.location)
accept it in listener i.e. finish_control = check_url(url)

Note - Do not use global as it leads to security vulnerabilities

answered Mar 30 '15 at 19:32

Bhargav Rao

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returning always beats global – Padraic Cunningham Mar 30 '15 at 19:35
I know you guys are the experts, but could you explain why the language feature exists if it is not secure. I mean why are globals, eval, etc. not considered safe. I mean if a programmer adheres to what they have in mind there should never be a crash in the program, right? – Malik Brahimi Mar 30 '15 at 19:36
@MalikBrahimi Refer http://stackoverflow.com/questions/19158339/python-why-are-global-variables-evil – Bhargav Rao Mar 30 '15 at 19:38

While true loop not ending

2 Answers2