python主要是通過thread和threading這兩個模組來實現多執行緒支援。python的thread模組是比較底層的模組，python的threading模組是對thread做了一些封裝，可以更加方便的被使用。但是python（cpython）由於gil的存在無法使用threading充分利用cpu資源，如果想充分發揮多核cpu的計算能力需要使用multiprocessing模組(windows下使用會有諸多問題)。
如果在對執行緒應用有較高的要求時可以考慮使用stackless python來完成。stackless python是python的乙個修改版本，對多執行緒程式設計有更好的支援，提供了對微執行緒的支援。微執行緒是輕量級的執行緒，在多個執行緒間切換所需的時間更多，占用資源也更少。
通過threading模組建立新的執行緒有兩種方法：一種是通過threading.thread(target=executable method)-即傳遞給thread物件乙個可執行方法（或物件）;第二種是繼承threading.thread定義子類並重寫run()方法。第二種方法中，唯一必須重寫的方法是run()，可根據需要決定是否重寫__init__()。值得注意的是，若要重寫__init__()，父類的__init__()必須要在函式第一行呼叫，否則會觸發錯誤「assertionerror: thread.__init__() not called」
import threading
import time
class mythread(threading.thread):
def __init__(self,stopevt = none,file=none,name = 'subthread',type ='event'):
threading.thread.__init__(self)
self.stopevt = stopevt
self.name = name
self.file = file
self.type = type
def eventrun(self):
while not self.stopevt.isset():
print self.name +' alive\n'
time.sleep(2)
if self.file:
print 'close opened file in '+self.name+'\n'
self.file.close()
print self.name +' stoped\n'
def daemonrun(self):
d = mythreaddaemon(self.file)
d.setdaemon(true)
while not self.stopevt.isset():
print self.name +' alive\n'
time.sleep(2)
print self.name +' stoped\n'
def run(self):
if self.type == 'event': self.eventrun()
else: self.daemonrun()
class mythreaddaemon(threading.thread):
def __init__(self,file=none,name = 'daemonthread'):
threading.thread.__init__(self)
self.name = name
self.file = file
def run(self):
while true:
print self.name +' alive\n'
time.sleep(2)
if self.file:
print 'close opened file in '+self.name+'\n'
self.file.close()
print self.name +' stoped\n'
def evtstop():
stopevt = threading.event()
filea = open('testa.txt','w')
fileb = open('testb.txt','w')
a = mythread(stopevt,filea,'subthreada')
b = mythread(stopevt,fileb,'subthreadb')
print repr(threading.currentthread())+'alive\n'
print filea.name + ' closed? '+repr(filea.closed)+'\n'
print fileb.name + ' closed? '+repr(fileb.closed)+'\n'
a.start()
b.start()
time.sleep(1)
print repr(threading.currentthread())+'send stop signal\n'
stopevt.set()
a.join()
b.join()
print repr(threading.currentthread())+'stoped\n'
print 'after a stoped, '+filea.name + ' closed? '+repr(filea.closed)+'\n'
print 'after a stoped, '+fileb.name + ' closed? '+repr(fileb.closed)+'\n'
def daemonstop():
stopevt = threading.event()
filea = open('testa.txt','r')
a = mythread(stopevt,filea,'subthreada',type = 'daemon')
print repr(threading.currentthread())+'alive\n'
print filea.name + ' closed? '+repr(filea.closed)+'\n'
a.start()
time.sleep(1)
stopevt.set()
a.join()
print repr(threading.currentthread())+'stoped\n'
print 'after a stoped, '+filea.name + ' closed? '+repr(filea.closed)+'\n'
if not filea.closed:
print 'you see the differents, the resource in subthread may not released with setdaemon()'
filea.close()
if __name__ =='__main__':
print '-------stop subthread example with event:----------\n'
evtstop()
print '-------daemon stop subthread example :----------\n'
daemonstop()
執行結果是：
-------stop subthread example with event:----------
<_mainthread(mainthread, started 2436)>alive
testa.txt closed? false
testb.txt closed? false
subthreada alive
subthreadb alive
<_mainthread(mainthread, started 2436)>send stop signal
close opened file in subthreada
close opened file in subthreadb
subthreada stoped
subthreadb stoped
<_mainthread(mainthread, started 2436)>stoped
after a stoped, testa.txt closed? true
after a stoped, testb.txt closed? true
-------daemon stop subthread example :----------
<_mainthread(mainthread, started 2436)>alive
testa.txt closed? false
subthreada alive
subthreada stoped
<_mainthread(mainthread, started 2436)>stoped
after a stoped, testa.txt closed? false
you see the differents, the resource in subthread may not released with setdaemon()
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