(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 10—100 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.
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