Python threading.Timer only repeats once

Question

def On_Instrumentation_StartAnimation():  

    """
    Syntax      : On_Instrumentation_StartAnimation()
    Purpose     : Fired if the animation is started
    Parameters  : None
    """
    print "----------------------------------------------------------------------------------------"
    localtime = time.asctime(time.localtime(time.time()))
    global start
    start = time.clock()
    print "The user entered Animation Mode at local time: ", localtime
    print("This data has also been written to 'c:\dSPACE71\cdlog\cdlog.txt'")   
    threading.Timer(2, ExecuteDemo).start()
    ExecuteDemo()
    # Printing to the text file
    file1 = open('c:\dSPACE71\cdlog\cdlog.txt', 'a')
    file1.write("\n----------------------------------------------------------------------------------------")
    file1.write("\nThe user entered Animation Mode at local time: ")
    file1.write(localtime)
    file1.close()      

def ExecuteDemo()
    .
    .
    .
    Current_value = Current.Read()
    localtime = time.asctime(time.localtime(time.time()))
    print "The current reading at localtime:", localtime, "is", str(Current_value) + "."
    # Printing to the text file
    file1 = open('c:\dSPACE71\cdlog\cdlog.txt', 'a')
    file1.write("\n----------------------------------------------------------------------------------------")
    file1.write("\nThe current reading at localtime: ")
    file1.write(localtime)
    file1.write(" is: ")
    file1.write(str(Current_value))
    file1.close()
    .
    .
    .

As you can hopefully see, I'm trying to repeat the ExecuteDemo() function every 2 seconds after the StartAnimation function is called. But my problem here is that my ExecuteDemo() only runs twice. How can I get it to keep repeating? Am I missing something?

Answer 1

From the documentation:

class threading.Timer

A thread that executes a function after a specified interval has passed.

This means Threading.Timer will call a function after a specified period of time. And as you noticed, it gets called only once. The solution here will to have the timer set once again at the end of the ExecuteDemo(..) function.

def ExecuteDemo():
    .
    .
    .
    threading.Timer(2, ExecuteDemo).start()

---

In my opinion, the above method is a little inefficient. It is like every 2 seconds a new thread is being created, and once it executes the function, it dies before creating the next thread.

I would suggest something like this:

def ExecuteDemoCaller():
    #while True: # or something..
    while someCondition:
        ExecuteDemo()
        time.sleep(2)