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


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
 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.

Core Modules

More Standard Modules

Threads and Processes

Data Representation

File Formats

Mail and News Message Processing

Network Protocols


Multimedia Modules

Data Storage

Tools and Utilities

Platform-Specific Modules

Implementation Support Modules

Other Modules

Python Standard Library
Python Standard Library (Nutshell Handbooks) with
ISBN: 0596000960
EAN: 2147483647
Year: 2000
Pages: 252
Authors: Fredrik Lundh © 2008-2020.
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