from __future__ import print_function
import threading
def counter(count):
while count > 0:
print("Count value", count)
count -= 1
return
t1 = threading.Thread(target=countdown,args=(10,))
t1.start()
t2 = threading.Thread(target=countdown,args=(20,))
t2.start()
In certain implementations of Python such as CPython, true parallelism is not achieved using threads because of using what is known as the GIL, or Global Interpreter Lock.
Here is an excellent overview of Python concurrency:
Python concurrency by David Beazley (YouTube)