Python 基礎線程
#!/usr/bin/python
# -*- coding: UTF-8 -*-
import threading
import time
exitFlag = 0
class myThread(threading.Thread): # 繼承父類threading.Thread
def __init__(self, threadID, name, counter):
threading.Thread.__init__(self)
self.threadID = threadID
self.name = name
self.counter = counter
def run(self): # 把要執行的代碼寫到run函數裏面 線程在創建後會直接運行run函數
print "Starting " + self.name
print_time(self.name, self.counter, 5)
print "Exiting " + self.name
def print_time(threadName, delay, counter):
while counter:
if exitFlag:
(threading.Thread).exit()
time.sleep(delay)
print "%s: %s" % (threadName, time.ctime(time.time()))
counter -= 1
# 創建新線程
thread1 = myThread(1, "Thread-1", 1)
thread2 = myThread(2, "Thread-2", 2)
# 開啓線程
thread1.start()
thread2.start()
print "Exiting Main Thread"運行結果
Starting Thread-1
Starting Thread-2Exiting Main Thread
Thread-1: Mon Jul 19 14:02:18 2021
Thread-2: Mon Jul 19 14:02:19 2021Thread-1: Mon Jul 19 14:02:19 2021
Thread-1: Mon Jul 19 14:02:20 2021
Thread-1: Mon Jul 19 14:02:21 2021
Thread-2: Mon Jul 19 14:02:21 2021
Thread-1: Mon Jul 19 14:02:22 2021
Exiting Thread-1
Thread-2: Mon Jul 19 14:02:23 2021
Thread-2: Mon Jul 19 14:02:25 2021
Thread-2: Mon Jul 19 14:02:27 2021
Exiting Thread-2
Process finished with exit code 0
線程鎖
#!/usr/bin/python
# -*- coding: UTF-8 -*-
# 如果多個線程共同對某個數據修改，則可能出現不可預料的結果，爲了保證數據的正確性，需要對多個線程進行同步。
#
# 使用Thread對象的Lock和Rlock可以實現簡單的線程同步，這兩個對象都有acquire方法和release方法，對於那些需要每次只允許一個線程操作的數據，可以將其操作放到acquire和release方法之間。如下：
#
# 多線程的優勢在於可以同時運行多個任務（至少感覺起來是這樣）。但是當線程需要共享數據時，可能存在數據不同步的問題。
#
# 考慮這樣一種情況：一個列表裏所有元素都是0，線程"set"從後向前把所有元素改成1，而線程"print"負責從前往後讀取列表並打印。
#
# 那麼，可能線程"set"開始改的時候，線程"print"便來打印列表了，輸出就成了一半0一半1，這就是數據的不同步。爲了避免這種情況，引入了鎖的概念。
#
# 鎖有兩種狀態——鎖定和未鎖定。每當一個線程比如"set"要訪問共享數據時，必須先獲得鎖定；如果已經有別的線程比如"print"獲得鎖定了，那麼就讓線程"set"暫停，也就是同步阻塞；等到線程"print"訪問完畢，釋放鎖以後，再讓線程"set"繼續。
#
# 經過這樣的處理，打印列表時要麼全部輸出0，要麼全部輸出1，不會再出現一半0一半1的尷尬場面。
import threading
import time
class myThread(threading.Thread):
def __init__(self, threadID, name, counter):
threading.Thread.__init__(self)
self.threadID = threadID
self.name = name
self.counter = counter
def run(self):
print "Starting " + self.name
# 獲得鎖，成功獲得鎖定後返回True
# 可選的timeout參數不填時將一直阻塞直到獲得鎖定
# 否則超時後將返回False
threadLock.acquire()
print_time(self.name, self.counter, 3)
# 釋放鎖
threadLock.release()
def print_time(threadName, delay, counter):
while counter:
time.sleep(delay)
print "%s: %s" % (threadName, time.ctime(time.time()))
counter -= 1
threadLock = threading.Lock()
threads = []
# 創建新線程
thread1 = myThread(1, "Thread-1", 1)
thread2 = myThread(2, "Thread-2", 2)
# 開啓新線程
thread1.start()
thread2.start()
# 添加線程到線程列表
threads.append(thread1)
threads.append(thread2)
# 等待所有線程完成
for t in threads:
t.join()
print "Exiting Main Thread"運行結果
Starting Thread-1
Starting Thread-2
Thread-1: Mon Jul 19 14:07:59 2021
Thread-1: Mon Jul 19 14:08:00 2021
Thread-1: Mon Jul 19 14:08:01 2021
Thread-2: Mon Jul 19 14:08:03 2021
Thread-2: Mon Jul 19 14:08:05 2021
Thread-2: Mon Jul 19 14:08:07 2021
Exiting Main Thread
Process finished with exit code 0隊列
#!/usr/bin/python
# -*- coding: UTF-8 -*-
import Queue
import threading
import time
exitFlag = 0
class myThread(threading.Thread):
def __init__(self, threadID, name, q):
threading.Thread.__init__(self)
self.threadID = threadID
self.name = name
self.q = q
def run(self):
print "Starting " + self.name
process_data(self.name, self.q)
print "Exiting " + self.name
def process_data(threadName, q):
while not exitFlag:
queueLock.acquire()
if not workQueue.empty():
data = q.get()
queueLock.release()
print "%s processing %s" % (threadName, data)
else:
queueLock.release()
time.sleep(1)
threadList = ["Thread-1", "Thread-2", "Thread-3"]
nameList = ["One", "Two", "Three", "Four", "Five"]
queueLock = threading.Lock()
workQueue = Queue.Queue(10)
threads = []
threadID = 1
# 創建新線程
for tName in threadList:
thread = myThread(threadID, tName, workQueue)
thread.start()
threads.append(thread)
threadID += 1
# 填充隊列
queueLock.acquire()
for word in nameList:
workQueue.put(word)
queueLock.release()
# 等待隊列清空
while not workQueue.empty():
pass
# 通知線程是時候退出
exitFlag = 1
# 等待所有線程完成
for t in threads:
t.join()
print "Exiting Main Thread"運行結果
Starting Thread-1
Starting Thread-2
Starting Thread-3
Thread-3 processing One
Thread-1 processing Two
Thread-3 processing Three
Thread-2 processing Four
Thread-1 processing Five
Exiting Thread-3
Exiting Thread-2
Exiting Thread-1
Exiting Main Thread
Process finished with exit code 0