python标准库介绍——31 threading 模块详解

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threading 模块     (可选) ``threading`` 模块为线程提供了一个高级接口, 如 [Example 3-1 #eg-3-1] 所示. 它源自 Java 的线程实现. 和低级的 ``thread`` 模块相同, 只有你在编译解释器时打开了线程支持才可以使用它 .   你只需要继承 //Thread// 类, 定义好 ``run`` 方法, 就可以创建一 个新的线程. 使用时首先创建该类的一个或多个实例, 然后调用 ``start`` 方法. 这样每个实例的 ``run`` 方法都会运行在它自的线程里.    ====Example 3-1. 使用 threading 模块====[eg-3-1]   ``` 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?00 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   *B*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*b* ```   [Example 3-1 #eg-3-1] 使用了 //Lock// 对象来在全局 //Counter// 对象里创建临界区 (critical section). 如果删除了 ``acquire`` 和 ``release`` 语句, 那么 ``Counter`` 很可能不会到达 100.