The threading Module

(Optional) The threading module is a higher-level interface for threading, demonstrated in Example 3-1. It's modeled after the Java thread facilities. Like the lower-level thread module, it's only available if your interpreter was built with thread support.

To create a new thread, subclass the Thread class and define the run method. To run such threads, create one or more instances of that class, and call the start method. Each instance's run method will execute in its own thread.

Example 3-1. Using the threading Module

File: threading-example-1.py import threading import time, random class Counter: def _ _init_ _(self): self.lock = threading.Lock() self.value = 0 def increment(self): self.lock.acquire() # critical section self.value = value = self.value + 1 self.lock.release() return value counter = Counter() class Worker(threading.Thread): def run(self): for i in range(10): # pretend we're doing something that takes 10100 ms value = counter.increment() # increment global counter time.sleep(random.randint(10, 100) / 1000.0) print self.getName(), "-- task", i, "finished", value # # try it for i in range(10): Worker().start() # start a worker Thread-1 -- task 0 finished 1 Thread-3 -- task 0 finished 3 Thread-7 -- task 0 finished 8 Thread-1 -- task 1 finished 7 Thread-4 -- task 0 Thread-5 -- task 0 finished 4 finished 5 Thread-8 -- task 0 Thread-6 -- task 0 finished 9 finished 6 ... Thread-6 -- task 9 finished 98 Thread-4 -- task 9 finished 99 Thread-9 -- task 9 finished 100

Example 3-1 also uses Lock objects to create a critical section inside the global counter object. If you remove the calls to acquire and release, it's pretty likely that the counter won't reach 100.