I'm having some problems declaring a list. It seems like I cannot delete all the elements in the list. At the reset_a printout, it display an empty list but after another around of checking the list in myFunction, the previous element is still in the list. How can I  declare a global list and use it all over others defined?
a = []
def reset_a():
    global a
    del a[:]
    print a
def myFunction():
     global a
     #check other stuffs........... then..
     print a
     if data not in a:
         a.append(data)
         time.sleep(5)
         reset_a()
if __name__=='__main__':
     while True:
        myFunction()
Edited: I found a way to get it done.
global a
a = []
def reset_a():
    del a[:]
    print a
def myFunction():
     #check other stuffs...........and get 'data' then..
     print a
     if data not in a:
         a.append(data)
         time.sleep(5)
         reset_a()
if __name__=='__main__':
     while True:
        myFunction()
 
    