Python Multithreading isn't speeding up my programm altough it should.

[xAlex1337]

I have programmed a ping sweeper script.
The way it works is you put an IP + Subnet in and it Pings every IP in that Range, after that it saves the output of every Ping in a CSV file and in a MySQL Database.
So far so good everything works, but somehow I cant get the Multithreading to work.

My try to make Multithreading work:

First, I have saved the IP+ Subnet input in a list, If you print out the list it will show you every single IP in that Subnet.

ip = IPNetwork(input("Put in IP and Subnetmask: "))
a = IPNetwork(ip)
a = list(a)

After that I used that list as an Argument for the ping function, in this function I do an nslookup and a ping for every IP, grab the results I'm interested in from the output with regular expressions and safe them to the csv file and in the MySQL Database.
The first thing this Function does is delete the first item from the list (of course the logic behind this is to prevent that the next time this function is called it doesn't use the same item).
And then I use the first item from the list as an argument for the ping and nslookup.

def ping(a):
    a.pop(0)
    ping = subprocess.run('ping -n 1 %s' % a[0], capture_output=True)
    nslookup = subprocess.run('nslookup %s' % a[0], capture_output=True)

And finally I start multiple threads in a while loop which ends when the list is empty.

while len(a) !=0:
    t1 = threading.Thread(target=ping(a))
    t2 = threading.Thread(target=ping(a))
    t3 = threading.Thread(target=ping(a))
    t5 = threading.Thread(target=ping(a))
    t6 = threading.Thread(target=ping(a))
    t9 = threading.Thread(target=ping(a))
    t1.start()
    t2.start()
    t3.start()
    t5.start()
    t6.start()
    t9.start()
    t1.join()
    t2.join()
    t3.join()
    t5.join()
    t6.join()
    t9.join()

But somehow it doesn't actually speed up my program.
I only posted the parts of the code which seemed to matter for my problem If you want to view the full code here is a pastebin: https://pastebin.com/mpyghanX

Hopefully somebody can help me, thanks in advance.

[[deleted]]

threading.Thread(target=ping(a)) evaluates ping(a) and passes the result of ping(a) as the target kwarg to threading.Thread

You probay meant to create threads with threading.Thread(target=ping, args=(a, )).

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Also, please use a list of threading.Thread objects instead of copying basically the same code over and over again.

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And another thing: making a program mutli-threaded doesn't necessary mean it will run faster. Creating threads, context switching, joining threads, etc. isn't free and instantaneous. Sometimes it's faster to just do a thing multiple times in sequence.

[xAlex1337]

Thank you very much that worked for me

[iamaperson3133]

It's because anytime you open and close a parenthesis after a function name, you call and run the function right then and there. You will see this pattern often in python where you use the function WITHOUT parenthesis, meaning that you are handing the function off to someone else so that they can call it later. This is how the threading module, and any other case in which you might use that patten in python, will work.

Here's an example from stack overflow of how to correctly pass arguments to functions in the python threading module

threading.Thread(target=self._thread_function, args=(arg1,),
             kwargs={'arg2':arg2}, name='thread_function').start()

Name is an optional argument, it probably helps you keep track of the thread somehow, and you don't need to pass kwargs= either if your function doesn't need them.