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?

• fedorqui: listener() function does not "know" the finish_control variable

Answer 1

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

global finish_control

• JayGatsby: i will mark it in few minutes it's not allow me now

Answer 2

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

• Padraic Cunningham: returning always beats global
• Malik Brahimi: 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?
• Bhargav Rao: @MalikBrahimi Refer stackoverflow.com/questions/19158339/…